window: Properly destroy tooltip windows when parent window is destroyed

If we destroy a window with an active tooltip, we leave the tooltip
hanging around.  Call tooltip destructor when destroying a window.
This fixes the stuck tooltip observed when unplugging a monitor with
an active tooltip on the panel.

Closes: https://bugs.freedesktop.org/show_bug.cgi?id=72931

clients/window.c

@@ -1653,10 +1653,8 @@ widget_destroy(struct widget *widget)
 	if (surface->widget == widget && surface->subsurface)
 		surface_destroy(widget->surface);
 
-	if (widget->tooltip) {
-		free(widget->tooltip);
-		widget->tooltip = NULL;
-	}
+	if (widget->tooltip)
+		widget_destroy_tooltip(widget);
 
 	wl_list_for_each(input, &display->input_list, link) {
 		if (input->focus_widget == widget)