Instead of copying the value returned by get_prop_name and then releasing it,
directly use the return value of get_prop_name, which allocates memory for the
name.

If get_prop_name returns NULL, continue on to XFreeFont to release the font
before returning the NULL via the normal function return.
Reviewed-by: Erkki Seppälä <erkki.seppala@vincit.fi>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Backported-to-NX-by: Ulrich Sibiller <uli42@gmx.de>