Suppress "variable may be used uninitialized" warning.

Suppress "variable may be used uninitialized" warning.

Buildfarm member caiman is showing this, which surprises me because
it's very late-model gcc (14.0.1) and ought to be smart enough to
know that elog(ERROR) doesn't return.  But we're likely to see the
same from stupider compilers too, so add a dummy initialization in
our usual style.