Redis [BUG]P otential error handling bugs

While reading the newest codes, I found several suspicious codes that could be potential error handling bugs.

I found that there are many variables with the data type "connection" whose member fd is used directly without being checked if they equal to -1.

To be specific, I found the above problem in the following functions: connSocketWrite, connSocketWritev, connSocketRead, connSocketEventHandler, connSocketAddr, connSendTimeout, connRecvTimeout, connCreateAcceptedUnix, connUnixSyncWrite, connUnixSyncReadLine, connSocketSyncWrite, connSocketSyncRead, connSocketSyncReadLine.

I understand that they are currently not in danger of triggering any error. I'm listing them in case you want to maintain it in the future.