Ensure unsubscription in the molecular viewer

Src/GUI/Plugins/MolecularViewerPlugin.py

@@ -251,12 +251,17 @@ class MolecularViewerPlugin(ComponentPlugin):
         
         self.SetFocusIgnoringChildren()
            
-    def close(self):
-                
+    def close(self):
+        # Ensure unsubscription
+        self.__unsubscribe()
+        # Clear the viewer
         self.clear_universe()
 
-    def __del__(self):
-        
+    def __del__(self):
+        # Ensure unsubscription
+        self.__unsubscribe()
+        
+    def __unsubscribe(self):
         PUBLISHER.unsubscribe(self.msg_set_selection, "msg_set_selection")
         PUBLISHER.unsubscribe(self.msg_switch_viewers_state, "msg_switch_viewers_state")
         PUBLISHER.unsubscribe(self.msg_clear_selection,'msg_clear_selection')