fix: clear popup state when it is dismissed by the compositor

cosmic-applet-graphics/src/window.rs

@@ -412,4 +412,8 @@ impl cosmic::Application for Window {
     fn style(&self) -> Option<<Theme as application::StyleSheet>::Style> {
         Some(cosmic::app::applet::style())
     }
+
+    fn on_close_requested(&self, id: window::Id) -> Option<Message> {
+        Some(Message::PopupClosed(id))
+    }
 }