Fixed another crash that occurred when double-clicking on the tab-bar but not on a tab.

wobuzz/ui/playlist_tabs/tab_bar.py

@@ -36,6 +36,10 @@ class PlaylistTabBar(QTabBar):
 
     def on_doubleclick(self, index):
         playlist_view = self.tab_widget.widget(index)
+
+        if playlist_view is None:  # dont crash if no playlist was double-clicked
+            return
+
         playlist = playlist_view.playlist
 
         if playlist.has_tracks():  # dont crash when playlist is empty