Last modified: 2014-02-12 23:54:05 UTC
http://en.wikipedia.org/w/api.php?action=mobileview&format=json&page=Main_Page§ions=references - expect an empty resultset, get a 500 instead. More problematic is http://en.wikipedia.org/w/api.php?action=mobileview&format=json&page=Main_Page§ions=0|references - expect to get contents of section 0, get a 500 instead.
The error message on the 500 is: PHP fatal error in /usr/local/apache/common-local/php-1.20wmf5/extensions/MobileFrontend/api/ApiMobileView.php line 117: Unsupported operand types
Yuvi submitted a fix in https://gerrit.wikimedia.org/r/#/c/12788/
Merged and deployed.