add some security checks to workaround in case Aple decides to change it's ivar names
add some security checks to workaround in case Aple decides to change it's ivar names

git-svn-id: 765db44a9620ed55f4f8addfd3c14fe8cd57f6bb@5687 0fceea05-a30d-0410-8a8b-80ef821fb0a1

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