Remove observer for file auto check pref when window will close rather than dealloc, as we may have not registered for this.
Remove observer for file auto check pref when window will close rather than dealloc, as we may have not registered for this.

git-svn-id: 765db44a9620ed55f4f8addfd3c14fe8cd57f6bb@3564 0fceea05-a30d-0410-8a8b-80ef821fb0a1

nanoant/Skim,nanoant/Skim,nanoant/Skim,nanoant/Skim,nanoant/Skim