fix for possible leak

git-svn-id: svn://svn.code.sf.net/p/machoview/code/trunk@237 48439af1-32ae-43fb-a04c-585ec6ffdf7c
do not return nil from init()

git-svn-id: svn://svn.code.sf.net/p/machoview/code/trunk@238 48439af1-32ae-43fb-a04c-585ec6ffdf7c
safer to remove observer on closing windows instead of deallocating

git-svn-id: svn://svn.code.sf.net/p/machoview/code/trunk@239 48439af1-32ae-43fb-a04c-585ec6ffdf7c