vimscal.xml: If the solar remove coefficient cannot be calculated then a...

vimscal.xml: If the solar remove coefficient cannot be calculated then a default value will be used now instead of giving an error 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@272 41f8697f-d340-4b68-9986-7bafba869bb8