pgsql: Fix WaitLatch(NULL) on Windows.

Fix WaitLatch(NULL) on Windows.

Further to commit 733fa9aa, on Windows when a latch is triggered but we
aren't currently waiting for it, we need to locate the latch's HANDLE
rather than calling ResetEvent(NULL).

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reported-by: Ranier Vilela <ranier.vf@gmail.com>
Discussion: https://postgr.es/m/CAEudQArTPi1YBc%2Bn1fo0Asy3QBFhVjp_QgyKG-8yksVn%2ByRTiw%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a7e65dc88b6f088fc2fcf5a660d866de644b1300

Modified Files
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src/backend/storage/ipc/latch.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)