What was your feedback ID number?
Have same issue after update to macOS Catalina 10.15.
How do you fixed this?
I had never recieved an email alerting me to the follow ups on this thread. Here's answers to both the followups:
I filed two reports. The first report was filed under "Developer Tools". The id for that is: FB6140383 - I thought that, perhaps, that was not the proper category, so I later filed it under, "macOS" with an id of: FB6162986
I have since worked around this issue, which I will explain below.
The workaround I used was simply creating the webview programatically rather than through the UI Builder. In fact, I stopped interacting with the UI Builder all together because just dragging a WebKit View (and subsequently doing nothing with it afterwards) caused all my extension tests to crash.
I am unsure if this bug still exists.