java.lang.RuntimeException: Unable to stop activity {org.fdroid.fdroid/org.fdroid.fdroid.views.AppDetailsActivity}: java.lang.NullPointerException: observer

ANDROID_VERSION: '9'
APP_VERSION_NAME: 1.5.1
AVAILABLE_MEM_SIZE: 89847042048
BRAND: google
DATE: '2019-01-20'
Message-ID: $2b$12$l3P2ynStKYnpWrBXNFyhN.FweBvGliIHt2wARFEhnNQw6dRduiqEi
PACKAGE_NAME: org.fdroid.fdroid
PHONE_MODEL: Pixel 3 XL
STACK_TRACE_HASH: ee70f5c1

STACK_TRACE:

java.lang.RuntimeException: Unable to stop activity 
{org.fdroid.fdroid/org.fdroid.fdroid.views.AppDetailsActivity}: 
java.lang.NullPointerException: observer 
  at android.app.ActivityThread.callActivityOnStop(ActivityThread.java:4189) 
  at 
android.app.ActivityThread.performStopActivityInner(ActivityThread.java:4159) 
  at android.app.ActivityThread.handleStopActivity(ActivityThread.java:4234) 
  at 
android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:192) 
  at 
android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:165) 
  at 
android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:142) 
  at 
android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816) 
  at android.os.Handler.dispatchMessage(Handler.java:106) 
  at android.os.Looper.loop(Looper.java:193) 
  at android.app.ActivityThread.main(ActivityThread.java:6718) 
  at java.lang.reflect.Method.invoke(Native Method) 
  at 
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
Caused by: java.lang.NullPointerException: observer 
  at 
com.android.internal.util.Preconditions.checkNotNull(Preconditions.java:128) 
  at 
android.content.ContentResolver.unregisterContentObserver(ContentResolver.java:1986) 
  at 
org.fdroid.fdroid.views.AppDetailsActivity.onStop(AppDetailsActivity.java:225) 
  at android.app.Instrumentation.callActivityOnStop(Instrumentation.java:1432) 
  at android.app.Activity.performStop(Activity.java:7375) 
  at android.app.ActivityThread.callActivityOnStop(ActivityThread.java:4181) 
... 13 more 
java.lang.NullPointerException: observer 
  at 
com.android.internal.util.Preconditions.checkNotNull(Preconditions.java:128) 
  at 
android.content.ContentResolver.unregisterContentObserver(ContentResolver.java:1986) 
  at 
org.fdroid.fdroid.views.AppDetailsActivity.onStop(AppDetailsActivity.java:225) 
  at android.app.Instrumentation.callActivityOnStop(Instrumentation.java:1432) 
  at android.app.Activity.performStop(Activity.java:7375) 
  at android.app.ActivityThread.callActivityOnStop(ActivityThread.java:4181) 
  at 
android.app.ActivityThread.performStopActivityInner(ActivityThread.java:4159) 
  at android.app.ActivityThread.handleStopActivity(ActivityThread.java:4234) 
  at 
android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:192) 
  at 
android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:165) 
  at 
android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:142) 
  at 
android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1816) 
  at android.os.Handler.dispatchMessage(Handler.java:106) 
  at android.os.Looper.loop(Looper.java:193) 
  at android.app.ActivityThread.main(ActivityThread.java:6718) 
  at java.lang.reflect.Method.invoke(Native Method) 
  at 
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

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