COMP: Fix unused variable warnings

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21984 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix sign comparison warning

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21985 3bd1e089-480b-0410-8dfb-8563597acbee