Fix NPE

build.gradle

@@ -14,7 +14,6 @@ buildscript {
 
 repositories {
     jcenter()
-    mavenCentral()
 }
 
 apply plugin: 'com.android.library'
@@ -48,6 +47,7 @@ android {
 
 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
+
     compile 'com.android.support:support-annotations:26.+'
     compile 'com.squareup.okhttp3:okhttp:3.8.1'
 

src/main/java/at/bitfire/dav4android/BasicDigestAuthHandler.kt

@@ -279,7 +279,7 @@ class BasicDigestAuthHandler(
     }
 
 
-    override fun authenticate(route: Route, response: Response) =
+    override fun authenticate(route: Route?, response: Response) =
             authenticateRequest(response.request(), response)
 
     override fun intercept(chain: Interceptor.Chain): Response {

src/test/java/at/bitfire/dav4android/BasicDigestAuthHandlerTest.java

@@ -258,4 +258,20 @@ public class BasicDigestAuthHandlerTest {
         assertNotNull(authenticator.digestRequest(original, authScheme));
     }
 
+    @Test
+    public void testAuthenticateNull() {
+        BasicDigestAuthHandler authenticator = new BasicDigestAuthHandler(null, "demo", "demo");
+        // must not crash (route may be null)
+        Request request = new Request.Builder()
+                .get()
+                .url("http://example.com")
+                .build();
+        Response response = new Response.Builder()
+                .request(request)
+                .protocol(Protocol.HTTP_2)
+                .code(200).message("OK")
+                .build();
+        authenticator.authenticate(null, response);
+    }
+
 }