Unable to access more than 50 messages

Hi. 

An user can't access messages of more than 50 users in [moodleroot]/message/index.php. We were expecting to have more messages loaded asynchronously when the user scrolls to the bottom of the list, but it doesn't seem to work (at least in Google Chrome, using the Boost and Classic themes). 

I've attached a video with the issue. In this example, the user has messages from 212 users, but can only access messages from 50 of them.