我正在开发 iphone 应用程序，它立即开始向我显示错误，无一例外，我真的很害怕这个错误，谁能告诉我为什么会这样？
<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.