Merge r3544: Lack of a backend name is no reasonable cause for a panic.

git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@3726 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_vrt.c

@@ -697,9 +697,10 @@ VRT_double_string(const struct sess *sp, double num)
 const char *
 VRT_backend_string(struct sess *sp)
 {
-       CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
-       CHECK_OBJ_NOTNULL(sp->director, DIRECTOR_MAGIC);
-       return (sp->director->vcl_name);
+	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
+	if (sp->director == NULL)
+		return (NULL);
+	return (sp->director->vcl_name);
 }
 
 /*--------------------------------------------------------------------*/