<http://trac.webkit.org/changeset/121482> fixed a class of undo-related bugs where undo entries were left on the stack after their target was dealloc’ed. This triggered a Lion-only crash closing an NSPopover that contains a WKView, due to an object lifetime bug in AppKit. This AppKit bug was fixed in OS X 10.8. This bug represents working around that AppKit bug in OS X 10.7. This is in Radar as <rdar://problem/12128557>.
Created attachment 159453 [details] Patch to avoid a line of recently-added code in the problematic case, only on OS X 10.7
Fixed in http://trac.webkit.org/changeset/126041