webView設置代理後，跳出This task has already been stopped

[pig320pig320]

請問我設置好代理後，進入網頁會報錯 *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This task has already been stopped' terminating with uncaught exception of type NSException 導致程式崩潰，請問是什麼原因呢？