Invalid timestamps on files caused mc to segfault by passing a null

  pointer to strftime. Avoid trying to print the time in this case.

  Reported by Maxim Britov <maxim@office.modum.by>

  at http://bugs.gentoo.org/184296

--- mc-4.6.1/src/util.c

+++ mc-4.6.1/src/util.c

@@ -717,6 +717,7 @@

     static size_t i18n_timelength = 0;

     static const char *fmtyear, *fmttime;

     const char *fmt;

+    struct tm *whentm;

     if (i18n_timelength == 0){

 	i18n_timelength = i18n_checktimelength() + 1;

@@ -740,7 +741,11 @@

     else

 	fmt = fmttime;

-    strftime (timebuf, sizeof (timebuf) - 1, fmt, localtime(&when));

+    whentm = localtime(&when);

+    if (whentm == NULL)

+	return "(invalid)";

+

+    strftime (timebuf, sizeof (timebuf) - 1, fmt, whentm);

     return timebuf;

 }