我收到一个奇怪的错误(EXC_BAD_ACCESSbyCFStringGetLengthwithinNSManagedObject(MagicalRecord)MR_executeFetchRequest:inContext:)当我尝试从JSON文件导入数据时，我无法理解...NSManagedObjectContext*opContext=[NSManagedObjectContextMR_contextForCurrentThread];NSString*jsonPath=[[NSBundlemainBundle]pathForResource:@"DefaultData"ofTy