prevent a GTK warning

src/groupchat_control.py

@@ -2159,6 +2159,9 @@ class GroupchatControl(ChatControlBase):
 				self.tooltip.hide_tooltip()
 
 	def show_tooltip(self, contact):
+		if not self.list_treeview.window:
+			# control has been destroyed since tooltip was requested
+			return
 		pointer = self.list_treeview.get_pointer()
 		props = self.list_treeview.get_path_at_pos(pointer[0], pointer[1])
 		# check if the current pointer is at the same path