[NbtkStylable] comment out unused variable to prevent compiler warning
[NbtkStylable] comment out unused variable to prevent compiler warning

This variable is used only in a commented out section of code, so it too
should be commented out.

clutter-project/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,clutter-project/mx