Fatal exception with overview button

Fatal exception when returning to the application from the overview button. Typical situation:

• Launch of Nextcloud Bookmarks
• Opening a bookmark to a browser
• Visit of the website
• Back to Nextcloud Bookmarks with overview button

Error Log from Android Studio

2023-03-21 19:40:44.824 4440-4471/org.bisw.nxbookmarks E/Perf: Fail to get file list org.bisw.nxbookmarks
2023-03-21 19:40:44.825 4440-4471/org.bisw.nxbookmarks E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2023-03-21 19:40:44.825 4440-4471/org.bisw.nxbookmarks E/Perf: Fail to get file list org.bisw.nxbookmarks
2023-03-21 19:40:44.825 4440-4471/org.bisw.nxbookmarks E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2023-03-21 19:40:45.510 4440-4440/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Prepare the API
2023-03-21 19:40:45.522 4440-4440/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Found user: ***********
2023-03-21 19:40:45.553 4440-4440/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Done!
2023-03-21 19:40:45.557 4440-4477/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: API is already set up, we can continue...
2023-03-21 19:40:45.561 4440-4477/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.REST.OCBookmarksRestConnector: API Root-Url: /index.php/apps/bookmarks/public/rest/v2
2023-03-21 19:40:45.685 4440-4440/org.bisw.nxbookmarks E/AndroidRuntime: FATAL EXCEPTION: main
    Process: org.bisw.nxbookmarks, PID: 4440
    java.lang.RuntimeException: Unable to resume activity {org.bisw.nxbookmarks/org.schabi.ocbookmarks.MainActivity}: java.lang.IllegalStateException: Fragment already added: BookmarkFragment{118b93b} (1b09d004-ddf8-4cc0-ae44-057cb24bff2a id=0x7f080087)
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4206)
        at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4238)
        at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2017)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7397)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:935)
     Caused by: java.lang.IllegalStateException: Fragment already added: BookmarkFragment{118b93b} (1b09d004-ddf8-4cc0-ae44-057cb24bff2a id=0x7f080087)
        at androidx.fragment.app.FragmentStore.addFragment(FragmentStore.java:91)
        at androidx.fragment.app.FragmentManager.addFragment(FragmentManager.java:1713)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:415)
        at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2404)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2162)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:2002)
        at androidx.fragment.app.FragmentController.execPendingActions(FragmentController.java:451)
        at androidx.fragment.app.FragmentActivity.onResume(FragmentActivity.java:436)
        at org.schabi.ocbookmarks.MainActivity.onResume(MainActivity.java:243)
        at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1454)
        at android.app.Activity.performResume(Activity.java:7939)
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4196)
        at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4238) 
        at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52) 
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2017) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7397) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:935) 
2023-03-21 19:40:45.813 4481-4481/? E/isw.nxbookmark: Unknown bits set in runtime_flags: 0x8000
2023-03-21 19:40:46.809 4481-4516/org.bisw.nxbookmarks E/Perf: Fail to get file list org.bisw.nxbookmarks
2023-03-21 19:40:46.809 4481-4516/org.bisw.nxbookmarks E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2023-03-21 19:40:46.809 4481-4516/org.bisw.nxbookmarks E/Perf: Fail to get file list org.bisw.nxbookmarks
2023-03-21 19:40:46.809 4481-4516/org.bisw.nxbookmarks E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
2023-03-21 19:40:47.453 4481-4481/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Prepare the API
2023-03-21 19:40:47.466 4481-4481/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Found user: ***********
2023-03-21 19:40:47.496 4481-4481/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: Done!
2023-03-21 19:40:47.499 4481-4522/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.MainActivity: API is already set up, we can continue...
2023-03-21 19:40:47.504 4481-4522/org.bisw.nxbookmarks E/class org.schabi.ocbookmarks.REST.OCBookmarksRestConnector: API Root-Url: /index.php/apps/bookmarks/public/rest/v2
2023-03-21 19:40:47.618 4481-4481/org.bisw.nxbookmarks E/AndroidRuntime: FATAL EXCEPTION: main
    Process: org.bisw.nxbookmarks, PID: 4481
    java.lang.RuntimeException: Unable to resume activity {org.bisw.nxbookmarks/org.schabi.ocbookmarks.MainActivity}: java.lang.IllegalStateException: Fragment already added: BookmarkFragment{118b93b} (1dce7c4a-d6f0-4516-b734-96e7c49987a9 id=0x7f080087)
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4206)
        at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4238)
        at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2017)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7397)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:935)
     Caused by: java.lang.IllegalStateException: Fragment already added: BookmarkFragment{118b93b} (1dce7c4a-d6f0-4516-b734-96e7c49987a9 id=0x7f080087)
        at androidx.fragment.app.FragmentStore.addFragment(FragmentStore.java:91)
        at androidx.fragment.app.FragmentManager.addFragment(FragmentManager.java:1713)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:415)
        at androidx.fragment.app.FragmentManager.executeOps(FragmentManager.java:2404)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2162)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:2002)
        at androidx.fragment.app.FragmentController.execPendingActions(FragmentController.java:451)
        at androidx.fragment.app.FragmentActivity.onResume(FragmentActivity.java:436)
        at org.schabi.ocbookmarks.MainActivity.onResume(MainActivity.java:243)
        at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1454)
        at android.app.Activity.performResume(Activity.java:7939)
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4196)
        at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4238) 
        at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52) 
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2017) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7397) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:935)