1、优化showLoading

lib/utils/loading_utils.dart

@@ -3,7 +3,7 @@ import 'package:flutter_easyloading/flutter_easyloading.dart';
 export 'package:flutter_easyloading/flutter_easyloading.dart';
 
 class LoadingUtils {
-  static void showLoading(String str) {
+  static void showLoading(String? str) {
     EasyLoading.show(status: str, maskType: EasyLoadingMaskType.black);
   }