r=troy, a=chofmann the editor's internal mDisplayFrame was not being removed from the frame manager's map of content->frames, so after enough scrolling in the addressing pane, reflow would try to reference a deleted frame. Fix is to remove the frame from the frame manager every time it's destroyed. git-svn-id: svn://10.0.0.236/trunk@56134 18797224-902f-48f8-a5cc-f745e15eee43