It's a well known issue. You can try to add a semicolon after the IP or if you want to reconnect just use "retry" or "reconnect"
It is time to go for the issue, since the guys are touching the code again.
I've updated the code to match the Source engine, you get a space appended only if the command you select doesn't already have one.
Nothing extracted yet.
This is true for the windows versions as well.
Sometimes you do a "connect 127.0.0.1" and when you disconnect and open the console, press up and press enter it will evaluate a "connect 127.0.0.1 ", which fails, because it will use the space in the address as well.
Please, either remove the trailing space from the completion or make connect ignore trailing spaces. I would go for the first one.
I thik this is a GoldSrc related problem in general.