wlr_scene: Initialize region32 before trying to use it

types/scene/wlr_scene.c

@@ -1497,6 +1497,7 @@ bool wlr_scene_output_commit(struct wlr_scene_output *scene_output) {
 	wlr_renderer_begin(renderer, output->width, output->height);
 
 	pixman_region32_t background;
+	pixman_region32_init(&background);
 	pixman_region32_copy(&background, &damage);
 
 	// Cull areas of the background that are occluded by opaque regions of