fix segfault caused by wrong pointer used in dbg()

TODO

@@ -1,3 +1,4 @@
+  o test --type=failed
   o add libudev queue - interface for /dev/.udev/queue/ state
       use queue interface for "settle"
       use queue interface for --type=failed

udev/udev_rules_parse.c

@@ -31,7 +31,7 @@
 
 void udev_rules_iter_init(struct udev_rules_iter *iter, struct udev_rules *rules)
 {
-	dbg(iter->rules->udev, "bufsize=%zi\n", rules->bufsize);
+	dbg(rules->udev, "bufsize=%zi\n", rules->bufsize);
 	iter->rules = rules;
 	iter->current = 0;
 }