Fix chkfont coredump on invalid input

Based on patch submitted by Kenneth Davies <kshrub@yahoo.com>
submitted in Debian bug #300735. Decrufted to provide double free()
fix, with minimal changes to FIGlet coding styles.

Bug-Debian: http://bugs.debian.org/300735

Signed-off-by: Jonathan McCrohan <jmccrohan@gmail.com>
Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>

chkfont.c

@@ -272,6 +272,7 @@ numsread=sscanf(fileline,"%c %d %d %d %d %d %d %d %d",
   &hardblank,&charheight,&upheight,&maxlen,&old_layout,&cmtcount,
   &ffrighttoleft,&layout,&spectagcnt);
 free(fileline);
+fileline = NULL;
 if (numsread<7) {
   ffrighttoleft=0;
   }