Enforce update nickname

Signed-off-by: Asai Neko <sugar@sne.moe>

service/service_user/update_user_info.go

@@ -39,7 +39,25 @@ func (self *UserServiceImpl) UpdateUserInfo(payload *UserInfoPayload) (result *U
 	}
 
 	if payload.Data.Nickname != nil {
-		if utf8.RuneCountInString(*payload.Data.Nickname) > 24 {
+		val := *payload.Data.Nickname
+		if val == "" {
+			execption := new(exception.Builder).
+				SetStatus(exception.StatusUser).
+				SetService(exception.ServiceUser).
+				SetType(exception.TypeCommon).
+				SetOriginal(exception.CommonErrorInvalidInput)
+
+			result = &UserInfoResult{
+				Common: shared.CommonResult{
+					HttpCode:  400,
+					Exception: execption,
+				},
+				Data: nil,
+			}
+
+			return
+		}
+		if utf8.RuneCountInString(val) > 24 {
 			execption := new(exception.Builder).
 				SetStatus(exception.StatusUser).
 				SetService(exception.ServiceUser).