Do not use deallocated instance ivars

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/apps/gworkspace/trunk@36015 72102866-910b-0410-8b05-ffd578937521
Fix memory leak by removing unnecessary retain self

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/apps/gworkspace/trunk@36016 72102866-910b-0410-8b05-ffd578937521