Skip direct scan-out commit when damage is empty

When there is no damage, no need to perform an output commit, even
when direct scan-out is used.

sway/desktop/output.c

@@ -556,6 +556,11 @@ static int output_repaint_timer_handler(void *data) {
 
 	wlr_output->frame_pending = false;
 
+	if (!wlr_output->needs_frame &&
+			!pixman_region32_not_empty(&output->damage_ring.current)) {
+		return 0;
+	}
+
 	struct sway_workspace *workspace = output->current.active_workspace;
 	if (workspace == NULL) {
 		return 0;
@@ -588,11 +593,6 @@ static int output_repaint_timer_handler(void *data) {
 		}
 	}
 
-	if (!output->wlr_output->needs_frame &&
-			!pixman_region32_not_empty(&output->damage_ring.current)) {
-		return 0;
-	}
-
 	int buffer_age;
 	if (!wlr_output_attach_render(output->wlr_output, &buffer_age)) {
 		return 0;