tinywl/tinywl: clean up tinywl_output when wlr_output is gone

Add destroy event processing.

Fixes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3416

tinywl/tinywl.c

@@ -73,6 +73,7 @@ struct tinywl_output {
 	struct tinywl_server *server;
 	struct wlr_output *wlr_output;
 	struct wl_listener frame;
+	struct wl_listener destroy;
 };
 
 struct tinywl_view {
@@ -549,6 +550,15 @@ static void output_frame(struct wl_listener *listener, void *data) {
 	wlr_scene_output_send_frame_done(scene_output, &now);
 }
 
+static void output_destroy(struct wl_listener *listener, void *data) {
+	struct tinywl_output *output = wl_container_of(listener, output, destroy);
+
+	wl_list_remove(&output->frame.link);
+	wl_list_remove(&output->destroy.link);
+	wl_list_remove(&output->link);
+	free(output);
+}
+
 static void server_new_output(struct wl_listener *listener, void *data) {
 	/* This event is raised by the backend when a new output (aka a display or
 	 * monitor) becomes available. */
@@ -582,6 +592,11 @@ static void server_new_output(struct wl_listener *listener, void *data) {
 	/* Sets up a listener for the frame notify event. */
 	output->frame.notify = output_frame;
 	wl_signal_add(&wlr_output->events.frame, &output->frame);
+
+	/* Sets up a listener for the destroy notify event. */
+	output->destroy.notify = output_destroy;
+	wl_signal_add(&wlr_output->events.destroy, &output->destroy);
+
 	wl_list_insert(&server->outputs, &output->link);
 
 	/* Adds this to the output layout. The add_auto function arranges outputs