ieee1275: Fix segfault in grub-ofpathname

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

util/ieee1275/grub-ofpathname.c

@@ -46,7 +46,9 @@ int main(int argc, char **argv)
     }
 
   of_path = grub_util_devname_to_ofpath (argv[1]);
-  printf("%s\n", of_path);
+
+  if (of_path)
+    printf ("%s\n", of_path);
 
   free (of_path);