E.g. http://fr.wikipedia.org/w/api.php?action=feedcontributions&user=Apokrif&feedformat=atom
2014-12-24 12:37:46 mw1233 frwiki: [a454b3c5] /w/api.php?action=feedcontributions&user=Apokrif&feedformat=atom MWException from line 354 of /srv/mediawiki/php-1.25wmf12/extensions/Flow/includes/Formatter/AbstractQuery.php: Accessing non-existent parameter: page_namespace
#0 /srv/mediawiki/php-1.25wmf12/includes/api/ApiFeedContributions.php(106): Flow\Formatter\FormatterRow->__get()
#1 /srv/mediawiki/php-1.25wmf12/includes/api/ApiFeedContributions.php(98): ApiFeedContributions->feedItem()
#2 /srv/mediawiki/php-1.25wmf12/includes/api/ApiMain.php(954): ApiFeedContributions->execute()
#3 /srv/mediawiki/php-1.25wmf12/includes/api/ApiMain.php(392): ApiMain->executeAction()
#4 /srv/mediawiki/php-1.25wmf12/includes/api/ApiMain.php(363): ApiMain->executeActionWithErrorHandling()
#5 /srv/mediawiki/php-1.25wmf12/api.php(85): ApiMain->execute()
#6 /srv/mediawiki/w/api.php(3): include()
#7 {main}
there are 5 of these in the log from frwiki, metawiki, enwiki.