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Notice: Undefined property: stdClass::$backupsize in /var/www/moodle/blocks/community/renderer.php on line 263

This is due to the hub web service function get_courses that sometimes does not return a backup size for the downloadable course:
a) it should always return a backup size
b) if the backup size is equal to zero so we may not want to return the downloadable course at all
c) I suspect that it currently fail for backupsize < 1Mb. I checked, one of the course not receiving backupsize has a size of 0.15Mb.