sizeof(Thread.Queue()) is not equal to Thread.Queue()->size().
Fixes the calculation for adaptive buffer refills.
Without this fix, it *will* result in hung queries, but only
if the number of rows returned exceeds 1024.

- Solves the last remaining one-deadlock-per-month problem.
- Speeds up the critical path with regard to stash-flushing.

Depending on timing when the query finishes, there can be
multiple internal EOF rows.