rootston: Don't let the wlr_output handle the fullscreen view in case of layer-shell overlays

Otherwise the overlays will no tbe drawn.

Closes: #1300
(cherry picked from commit 175ccc25179f75f20bd618172ae8156e137c3615)

rootston/output.c

@@ -423,7 +423,8 @@ static void render_output(struct roots_output *output) {
 			output_box->y;
 		view_move(view, view_x, view_y);
 
-		if (has_standalone_surface(view)) {
+		if (has_standalone_surface(view) &&
+				wl_list_empty(&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY])) {
 			wlr_output_set_fullscreen_surface(wlr_output, view->wlr_surface);
 		} else {
 			wlr_output_set_fullscreen_surface(wlr_output, NULL);