Fix an issue with duplicate calls

Signed-off-by: Mario Danic <mario@lovelyhq.com>

app/gplay.gradle

@@ -1,8 +1,4 @@
-ext {
-    googleLibraryVersion = '9.6.1'
-}
-
 dependencies {
-  implementation "com.google.android.gms:play-services-gcm:${googleLibraryVersion}"
-  implementation "com.google.firebase:firebase-messaging:${googleLibraryVersion}"
+  implementation "com.google.android.gms:play-services-gcm:15.0.1"
+  implementation "com.google.firebase:firebase-messaging:17.1.0"
 }

app/src/gplay/java/com/nextcloud/talk/services/firebase/MagicFirebaseMessagingService.java

@@ -34,6 +34,10 @@ public class MagicFirebaseMessagingService extends FirebaseMessagingService {
     @SuppressLint("LongLogTag")
     @Override
     public void onMessageReceived(RemoteMessage remoteMessage) {
+        if (remoteMessage == null) {
+            return;
+        }
+
         if (remoteMessage.getData() != null) {
             PersistableBundleCompat persistableBundleCompat = new PersistableBundleCompat();
             persistableBundleCompat.putString(BundleKeys.KEY_NOTIFICATION_SUBJECT, remoteMessage.getData().get