Fixed an error in hist where running the application from the command line...

Fixed an error in hist where running the application from the command line without a TO parameter entered, the application would process the histogram and then throw an error after telling the user they needed a TO argument. Fixes #3914.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@6789 41f8697f-d340-4b68-9986-7bafba869bb8