App crash when UITextField is open

I am using a WKWebView to load a webpage and a UITextFiled as the address bar. If I select the UITextField and try to click out of it on to the webView my app crashes. Only happens after textField has been selected. I can navigate other buttons fine. I feel its something obvious but I am new to Swift.
I get "terminating with uncaught exception of type NSException" then it takes me to the appDelegate page.
Please file a Feedback Assistant issue and post the FBnnnnnnnn ID here.

Include the crash log with the FB issue. (Probably not necessary to include a sysdiagnose, but a small Xcode project that reproudces the issue would also be useful.)

App crash when UITextField is open
 
 
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