The black wire/connection pictured below is a mystery to me. All electrical components are working, but it appears it was connected at some point. The wire comes from the black junction pictured, and a black wire comes out the other side with a blunt end, which doesn't appear to have ever been connected to anything. I assume it's a ground, but should it be attached to any place special (battery, frame, etc.), or just grounded anywhere? If not already apparent, I have zero knowledge when it come to electrical issues. This is my last "button down" issue in the refurb of my 77 r100rs, so I want to get it right. Any guidance will be appreciated!