Replace stb_vorbis with libogg+libvorbis

editor/editor_file_system.cpp

@@ -444,6 +444,10 @@ bool EditorFileSystem::_test_for_reimport(const String &p_path, bool p_only_impo
 
 	Ref<ResourceImporter> importer = ResourceFormatImporter::get_singleton()->get_importer_by_name(importer_name);
 
+	if (importer.is_null()) {
+		return true; // the importer has possibly changed, try to reimport.
+	}
+
 	if (importer->get_format_version() > version) {
 		return true; // version changed, reimport
 	}