These three are the only ones I know of with the null title problem:
http://www.fimfiction.net/api/story.php?story=51241,
http://www.fimfiction.net/api/story.php?story=52367 and
http://www.fimfiction.net/api/story.php?story=65474. It's really rare but I kept careful track of them because if one of these gets included in a batch update the whole batch fails.
I'll try out the attached version and let you know how it works for me. I haven't updated any of my actual I'm-reading-these stories with the latest update, just test data I can throw away, so there shouldn't be any misnamed chapters hidden away in hard-to-find places.
Oh, an unrelated question while on the subject of scraping pages and whatnot. FiMFiction stories sometimes have "sex" and "gore" tags on their description pages (
http://www.fimfiction.net/story/74526/ and
http://www.fimfiction.net/story/58005/ are examples). Does FFDL pick those up? I thought I'd hooked up all the metadata to custom columns but I've overlooked stuff like this before.
Edit: Just tried it out on that test case from yesterday and it worked great, chapters are titled correctly. Thanks! I wish you'd put a "donate" link on your plugin, after all this hassle "thanks" seems like such a minor reward.