Hide play queue button in VideoDetailsFragment mini player when the play queue is empty

Related PR introducing the button: #8946

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

@@ -248,6 +248,7 @@ public final class VideoDetailFragment
             autoPlayEnabled = true; // forcefully start playing
             openVideoPlayerAutoFullscreen();
         }
+        updateOverlayPlayQueueButtonVisibility();
     }
 
     @Override
@@ -337,6 +338,8 @@ public final class VideoDetailFragment
 
         activity.sendBroadcast(new Intent(ACTION_VIDEO_FRAGMENT_RESUMED));
 
+        updateOverlayPlayQueueButtonVisibility();
+
         setupBrightness();
 
         if (tabSettingsChanged) {
@@ -1820,6 +1823,14 @@ public final class VideoDetailFragment
                     + title + "], playQueue = [" + playQueue + "]");
         }
 
+        // Register broadcast receiver to listen to playQueue changes
+        // and hide the overlayPlayQueueButton when the playQueue is empty / destroyed.
+        if (playQueue != null && playQueue.getBroadcastReceiver() != null) {
+            playQueue.getBroadcastReceiver().subscribe(
+                    event -> updateOverlayPlayQueueButtonVisibility()
+            );
+        }
+
         // This should be the only place where we push data to stack.
         // It will allow to have live instance of PlayQueue with actual information about
         // deleted/added items inside Channel/Playlist queue and makes possible to have
@@ -1926,6 +1937,7 @@ public final class VideoDetailFragment
                     currentInfo.getUploaderName(),
                     currentInfo.getThumbnailUrl());
         }
+        updateOverlayPlayQueueButtonVisibility();
     }
 
     @Override
@@ -2392,6 +2404,18 @@ public final class VideoDetailFragment
         });
     }
 
+    private void updateOverlayPlayQueueButtonVisibility() {
+        final boolean isPlayQueueEmpty =
+                player == null // no player => no play queue :)
+                        || player.getPlayQueue() == null
+                        || player.getPlayQueue().isEmpty();
+        if (binding != null) {
+            // binding is null when rotating the device...
+            binding.overlayPlayQueueButton.setVisibility(
+                    isPlayQueueEmpty ? View.GONE : View.VISIBLE);
+        }
+    }
+
     private void updateOverlayData(@Nullable final String overlayTitle,
                                    @Nullable final String uploader,
                                    @Nullable final String thumbnailUrl) {