Do not error flood if removing default environment. Closes #9945

scene/main/scene_tree.cpp

@@ -542,6 +542,10 @@ bool SceneTree::idle(float p_time) {
 
 			if (env_path != String()) {
 				fallback = ResourceLoader::load(env_path);
+				if (fallback.is_null()) {
+					//could not load fallback, set as empty
+					ProjectSettings::get_singleton()->set("rendering/environment/default_environment", "");
+				}
 			} else {
 				fallback.unref();
 			}