Fix crash when closing video detail fragment

This bug started appearing because the way to close the player is now unified in PlayerHolder.stopService(), which causes the player to reach back to the video detail fragment with a notification of the shutdown (i.e. onServiceStopped() is called). This is fixed by adding a nullability check on the binding.

Author: Stypox

app/src/main/java/org/schabi/newpipe/fragments/detail/VideoDetailFragment.java

@@ -1848,13 +1848,16 @@ public void onPlayerError(final PlaybackException error, final boolean isCatchab
 
     @Override
     public void onServiceStopped() {
-        setOverlayPlayPauseImage(false);
-        if (currentInfo != null) {
-            updateOverlayData(currentInfo.getName(),
-                    currentInfo.getUploaderName(),
-                    currentInfo.getThumbnails());
+        // the binding could be null at this point, if the app is finishing
+        if (binding != null) {
+            setOverlayPlayPauseImage(false);
+            if (currentInfo != null) {
+                updateOverlayData(currentInfo.getName(),
+                        currentInfo.getUploaderName(),
+                        currentInfo.getThumbnails());
+            }
+            updateOverlayPlayQueueButtonVisibility();
         }
-        updateOverlayPlayQueueButtonVisibility();
     }
 
     @Override