Today I decided to clean my carpet and I take apart armrest assembly (boy was filthy in there) and besides parking brake (see picture below) there is a connector with missing cable. I tried to search for answer on my own but I felled - anybody knows what that is for?

 

Looks like a ground. If you're not getting any electrical noises and all your electronic components work, I wouldn't worry about it. Besides you've been driving around like that anyway