fix:

获取用户昵称头像bug修复

tr-framework/src/main/java/cn/tr/core/utils/UserUtil.java

@@ -21,6 +21,9 @@ public class UserUtil {
     public static Function<String, Pair<String,String>> userNickNameSupplier= userId->null;
 
     public static String getNickName(String userId){
+        if(StrUtil.isBlank(userId)){
+            return null;
+        }
         Pair<String, String> nickNameAndGender = getNickNameAndGender(userId);
         return ObjectUtil.isNull(nickNameAndGender)?null:nickNameAndGender.getKey();
     }
@@ -34,7 +37,7 @@ public class UserUtil {
 
     public static String getAvatar(String userId){
         if(StrUtil.isBlank(userId)){
-            return "";
+            return null;
         }
         Pair<String, String> nickNameAndGender = getNickNameAndGender(userId);
         if(nickNameAndGender==null){