[4/4] ntdll: Properly set flag which indicates buffer empty state.

[Dmitry Timoshkov]

Marvin <testbot at testbot.winehq.org> wrote:

> === WVISTAX64 (32 bit comm) ===
> comm.c:835: Test failed: WriteFile took 16 ms to write 0 Bytes at 150 Baud

Failure is not caused by this patch, probably a VM is very slow.

-- 
Dmitry.