Hi Blair and John,
This was reported with the 'Essential theme' information on the themes forum the other day -https://moodle.org/mod/forum/discuss.php?d=251951. This specific information allowed me to work out a fix. Please apply the 'format.php' fix you see in that thread.
In the fullness of time I'll release updated versions of CT from M2.5 onwards as it only affects users with the Essential theme. Humm, thinking about it, that's probably 70%+ of the Worlds Moodle sites given its global domination ;) - so will release sooner. Just give me time .