flockc: segfaults when file name is not given

$ flock -s
Segmentation fault

ltrace:
__libc_start_main(0x8048870, 2, 0xbfe9f404, 0x8049070, 0x8049060 <unfinished ...>
getopt_long(2, 0xbfe9f404, "+sexnouw:hV?", 0x80494e0, 0xbfe9f354) = 115
getopt_long(2, 0xbfe9f404, "+sexnouw:hV?", 0x80494e0, 0xbfe9f354) = -1
strtol(0, 0xbfe9f34c, 10, 0x80494e0, 0xbfe9f354 <unfinished ...>
--- SIGSEGV (Segmentation fault) ---
+++ killed by SIGSEGV +++

Addresses-Red-Had-Bugzilla: #489672
Signed-off-by: Karel Zak <kzak@redhat.com>

sys-utils/flock.c

@@ -217,7 +217,7 @@ int main(int argc, char *argv[])
 	   EX_NOINPUT);
     }
 
-  } else {
+  } else if (optind < argc) {
     /* Use provided file descriptor */
 
     fd = (int)strtol(argv[optind], &eon, 10);
@@ -226,8 +226,15 @@ int main(int argc, char *argv[])
       exit(EX_USAGE);
     }
 
+  } else {
+    /* Bad options */
+
+    fprintf(stderr, "%s: requires file descriptor, file or directory\n",
+		program);
+    exit(EX_USAGE);
   }
 
+
   if ( have_timeout ) {
     if ( timeout.it_value.tv_sec == 0 &&
 	 timeout.it_value.tv_usec == 0 ) {