Abort trap: 6 on Mac OSX Error

Hi There,

I'm hoping you please merge this rather trivial change in.  Unfortunately finding this was unbelievably difficult as I couldn't imagine the root of my issue was actually in a completion.  Long story aside..

I found an issue with the git bash completion on Mac OSX 10.8 using default bash where running certain commands [jam](http://www.perforce.com/resources/documentation/jam) would cause the command to give the non-informational `Abort trap: 6` error.

Please consider merging this in - and potentially saving the the rest of the planet from seeing or pulling their hair out for the 4 hours it took in debugging this!!


...range unrelated 'Abort trap: 6' error on non-git commands on Mac OSX 10.8.