"dig" crashes when interrupted while listening for UDP responses

To reproduce, fire up a dig query that will not get a response before it times out, e.g.:

dig @192.0.2.1 isc.org. A +time=10

and then hit CTRL+C:

dighost.c:4262: REQUIRE(isc_refcount_current(&recvcount) == 0) failed, back trace

It looks like current_lookup->q is empty in cancel_all() and thus the code block which decrements recvcount is not evaluated.