Both bugs surfaced when running protbot against a live Erupe instance.
LoadColumnWithDefault now treats an empty bytea ('\x', len 0) the same
as NULL. The postgres driver returns a non-nil empty slice for empty
bytea, so the prior `data == nil` check let a zero-byte slice reach
handleMsgMhfReceiveGachaItem, which forwarded it to the client as a
malformed gacha_items response. The MHF client interprets a zero-byte
count field as a protocol error and crashes the gacha menu, matching
the #175 symptom class. The handler also gains a defensive fallback
for len(data) == 0 in case another caller hits the same edge.
handleMsgMhfGetBoostTimeLimit was sending two ACKs for a single
request: doAckBufSucceed with the real payload, then an unconditional
doAckSimpleSucceed on the same ack handle. The second ACK was dead on
arrival (the handle was already consumed) but is a latent protocol
bug. Drop it and update the regression test that was asserting the
buggy 2-packet behavior.
8b2667f7a0