I was just getting ready to upgrade my production Moodle site. After upgrading my experimental site, I am getting the following warning messages (see graphic below). This seems to be related to the Topcoll plugin that I am using (Gareth). If I go to a course that is not using Topcoll, I do not get this message. Of course, I can not show this message by turning debug messages off, but this is why I leave it on.
Also, this is the first time that I am getting these error messages, they did not occur in Moodle 2.4+, only in Moodle 2.4.1+.
I might post this as a "bug" in tracker too, just in case it really has something to do with Moodle's code, and not Topcoll.