r57982 caused the showModalDialog() unit test to regress/crash.
This is caused by not always calling mainFrame() anymore, inside ChromeClientQt::createWindow. When returning from that function WebCore expects that a main frame exists.
Created attachment 54684 [details]
Committed r58485: <http://trac.webkit.org/changeset/58485>
Revision r58485 cherry-picked into qtwebkit-2.0 with commit 52345b219c57e8986cd399c148d85b7909a1dd6e
Sorry Simon, my patch causes the crash :( I will be careful next time