SmartMirror | An app to making an smart mirror from your old tablet

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[WKWebView view]: unrecognized selector sent to instance

As you probably know, this is because somebody is sending a -view message to your web view, which doesn't have a method by that name. UIViewController has such a method, though, so it's a good guess that somewhere in your app, your web view is being mistaken for a view controller. I don't see that happening in the code you posted, and it's hard to tell anything from just an image of a storyboard.

The way you can find the issue is to look at the stack trace when the error occurs. Find the thread where the exception is thrown, and then look down the stack for the one where the -view is called. That should show you what method is making the call. If the call isn't in your code, then look at the class involved... you should be able to at least get some clues as to what type of object is calling -view, and you can look at your code for the place where you configure that object.