Fix ios plugin always invalid due to null ConfigFile

Author: TCROC

editor/export/editor_export_platform_apple_embedded.h

@@ -288,7 +288,7 @@ class EditorExportPlatformAppleEmbedded : public EditorExportPlatform {
 			Vector<String> plugins_filenames = list_plugin_config_files(plugins_dir, true);
 
 			if (!plugins_filenames.is_empty()) {
-				Ref<ConfigFile> config_file;
+				Ref<ConfigFile> config_file = memnew(ConfigFile);
 				for (int i = 0; i < plugins_filenames.size(); i++) {
 					PluginConfigAppleEmbedded config = PluginConfigAppleEmbedded::load_plugin_config(config_file, plugins_dir.path_join(plugins_filenames[i]));
 					if (config.valid_config) {