fix mj任务失败信息是json，返回生成图片失败

midjourney/src/main/java/com/yhlxj/service/midjourney/impl/MidjourneyServiceImpl.java

@@ -1168,6 +1168,9 @@ public class MidjourneyServiceImpl implements MidjourneyService {
                 }
                 conversation.setProperties(jsonObject.toString());
             }
+            if(JSONUtil.isJson(conversation.getFailReason())){
+                conversation.setFailReason("生成图片失败");
+            }
 
             wssSession.sendMessage(WsMessageTypeEnum.SERVER_TASK_INFO, new JSONObject(conversation));
         }