If you enter fullscreen mode, type something in the address bar, force-click to look it up, and click away, then the window crashes.
When I try to replicate the bug in Safari, the address bar becomes part of the window title bar instead of crashing.
I expected the dictionary popup to disappear, and for the address bar text to remain.
(Like when you try to activate the bug while not in fullscreen)
1.1.1
Tahoe (26)