Since my last upgrade from 4.2 to 4.3, all my quizzes using random questions from empty categories (but which contain non-empty sub-categories) don't work anymore.

I get the following type of message:

"There are not enough questions in category 19 to create the question Random question (6107)."

I've tried creating new instances of the same quizzes with random questions from the same empty category and its non-empty subcategories, I find the selecting form a bit unpractical, but it works, and I noticed that the difference is in the mdl_question_set_references, more precisely the last field "filterconditions"

When it's from an old quiz, it contains things like:

and it doesn't work (see above error message)

When it's a new one, with questions randomly selected from the same category, it says:

{"filter":{"category":{"name":"category","jointype":1,"values":["19"],"filteroptions":

}},"cmid":4582,"courseid":68,"jointype":2,"qpage":0,"qperpage":1000,"sortdata":[],"cat":"19,25","tabname":"questions"}

And this time it works...

I hope this information helps fix the problem, as I will have to recreate manually a lot of quizzes!