Doing the following results in the assertion in -[WebFramePrivate setProvisionalDataSource:] (!d || !provisionalDataSource) failing: 1. Open a page that takes a few seconds to load. 2. While that page is loading, type a URL with a non-existent domain (such as http://apple.mac/) in the address bar and press Return. The assert is reached when Safari tries to load its HTML error page into the frame.
Created attachment 8883 [details] Proposed patch
I think Maciej should look at this.
Comment on attachment 8883 [details] Proposed patch I'm convinced. r=me
Committed revision 14910.