fix segfault in lutimes when tv argument is NULL

calling lutimes with tv=0 is valid if the application wants to set the
timestamps to the current time. this commit makes it so the timespec
struct is populated with values from tv only if tv != 0 and calls
utimensat with times=0 if tv == 0.

src/legacy/lutimes.c

@@ -6,9 +6,11 @@
 int lutimes(const char *filename, const struct timeval tv[2])
 {
 	struct timespec times[2];
-	times[0].tv_sec  = tv[0].tv_sec;
-	times[0].tv_nsec = tv[0].tv_usec * 1000;
-	times[1].tv_sec  = tv[1].tv_sec;
-	times[1].tv_nsec = tv[1].tv_usec * 1000;
-	return utimensat(AT_FDCWD, filename, times, AT_SYMLINK_NOFOLLOW);
+	if (tv) {
+		times[0].tv_sec  = tv[0].tv_sec;
+		times[0].tv_nsec = tv[0].tv_usec * 1000;
+		times[1].tv_sec  = tv[1].tv_sec;
+		times[1].tv_nsec = tv[1].tv_usec * 1000;
+	}
+	return utimensat(AT_FDCWD, filename, tv ? times : 0, AT_SYMLINK_NOFOLLOW);
 }