ResourceImporterScene: Add error when "default" is not defined to create clips

editor/import/resource_importer_scene.cpp

@@ -988,6 +988,7 @@ Ref<Animation> ResourceImporterScene::_save_animation_to_file(Ref<Animation> ani
 
 void ResourceImporterScene::_create_clips(AnimationPlayer *anim, const Array &p_clips, bool p_bake_all) {
 	if (!anim->has_animation("default")) {
+		ERR_FAIL_COND_MSG(p_clips.size() > 0, "To create clips, animations must be named \"default\".");
 		return;
 	}