TSIG-related named crash

Something bad happened here in the case system test (or, more specifically, after the case system test was finished):

01-Aug-2019 22:07:48.328 tsig.c:615: REQUIRE(ringp != ((void *)0) && *ringp != ((void *)0)) failed, back trace

Unfortunately, there is no core dump among job artifacts, which is not what I would expect. It may be related to the fact that this was an ASAN job (though this is not an ASAN-triggered crash, nor there is any ASAN-related output in the logs).

The obvious suspect is 3c30d095. @ondrej, any immediate ideas here?