Hi Ralf, it looks like anydbm and sqlite are working now
and you got mysql running. Really just a single line change?

I am surprised this bug didn't cause other
issues. If I entered -1 for unset in a search form would
that line be hit? If so would it work both before and after
your change?

I am pushing to CI now and will see how many times that line
is covered. I wonder if we have a test for -1 (unset) somewhere
in the test suite.

Nice find.