Well, then you are okay. Again, it's not a bug. It's just a simple message where one of your wireless clients cannot connect properly. Or, they attempt to and it fails. Having a MAC address of all 0's means that it didn't authenticate in the first place, otherwise a valid MAC would have been there.
Soo...do you have anything else trying to connect? Or scanning for your network, but doesn't now?
Either way, you are okay. You should be fine.