这些是IOS 7的bug吗？

我正在编写一个应用程序，它只提供一个带有文本字段的可编辑自定义单元格的表视图，当我进入编辑模式在单元格中输入文本时，我得到以下结果。但是，并不是每次我进入编辑模式时

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextSetStrokeColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextSaveGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextSetFlatness: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextAddPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextDrawPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939] <Error>: CGContextRestoreGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextSetFillColorWithColor:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextSetStrokeColorWithColor:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextSaveGState:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextSetFlatness:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextAddPath:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextDrawPath:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。
Jan 27 23:30:09 User-iMac.local SetList[5939]：CGContextRestoreGState:无效上下文0x0。这是一个严重的错误。此应用程序或其使用的库正在使用无效的上下文，从而导致系统稳定性和可靠性的整体降级。此通知是出于礼貌：请解决此问题。这将成为即将进行的更新中的致命错误。

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是的，请看这个类似的问题，我不认为这是一个iOS7错误。。。更重要的是，新版本的xCode中有一个bug。。。根据我的经验，它只影响模拟器。是的，同样的问题。我在发布之前用谷歌搜索了一下。