... or anything else with length = 0. This got broken in MDL-71696.
The only way to fix this kind-of involves and API change to
quiz_report_get_significant_questions. However, it is only changing
the external API of this function back to how it was before the 4.0 release,
and the chnages in 4.0 were never documented, nor, I would guess, intended,
since they just broke things.
* Support for old non-standard cron for quiz reports dropped. (Standard
cron support was added in 2.2
* Cron support added for qbehaviour, qformat and quizacces plugins.
* qtypes were already supported in the standard way.
