Yeah. You're right. Sorry the inconvenience of this mistake.

I've found the tag of my rss feed wasn't in the right place after several
days and forgot to close this issue. After that I didn't check the format
requirements of rss xml carefully though and just made a patch to fix it.
The original codes works well for all other feeds except the outlier I
tested at first(so unlucky!). Maybe it's quite rare for an rss xml to put
its tags in the wrong places.

Thanks for the reply. I should be more careful at testing.