parsePacketPayload copies message/msg_hash/sender_timestamp/attempt/txt_type from a
prior channels_log entry matched by pkt_hash. When that prior entry was logged while
the channel could not be decrypted it has none of those keys, so a later duplicate of
the same transmission raises KeyError: 'message' and aborts handle_rx for the whole
packet, dropping its RX_LOG_DATA. It triggers when a channel-table refresh lands
between two copies of a flooded channel message.
Copy with .get() so the fields are simply absent instead of raising. Adds a regression
test that reproduces the crash (fails on main, passes here).
