Fixed a bug when opening a recent project that caused the user to be prompted...

Fixed a bug when opening a recent project that caused the user to be prompted to save the project when no changes had been made. Fixes #5221.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/branches/ipce@8288 41f8697f-d340-4b68-9986-7bafba869bb8