FIX: catch exception


git-svn-id: https://www.nitrc.org/svn/cmtk/trunk@4994 42a5c34f-2066-0410-bec5-ba365beb4995
CHG: if input data is NULL, output is NULL


git-svn-id: https://www.nitrc.org/svn/cmtk/trunk@4995 42a5c34f-2066-0410-bec5-ba365beb4995