Fixed bug which caused qview to crash when closing viewports. This was...

Fixed bug which caused qview to crash when closing viewports.  This was related to the serial number list in MatchTool. Fixes #1130.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@4747 41f8697f-d340-4b68-9986-7bafba869bb8