Trying to save feed preferences when "feed categories" are turned off produces the following error:
Exception: TypeError?, fcat has no properties
Function: feedEditSave()
Location: prefs.js:679
Tracing the problem i found out that the problem is at tt-rss/prefs.js:feedEditSave()
It seems to use document.getElementById("iedit_fcat"); which as seen at tt-rss/backend.php: outputFeedList (at line 1507) is unavailable if ENABLE_FEED_CATS is set to false...
I'm referening to tt-rss-1.1.1.
Feel free to contact if you need more info
cyfex