You can disconnect if you like and feel better about it. It really isn't necessary, though. Pipe rigs weld on the back of the deck all the time and never have troubles. The electronics are on the front and the weld action is on the back. As long as the ground is connected to the work in the back and not on, say , the front bumper, the chances of current affecting the electronics is virtually nil. DC likes straight lines and short runs. That makes it easy.

FWIW, when they built my dump truck, about 75% of it was welded on the truck. The CAT computer never suffered and is still running strong. They did the same thing when they welded on the hitch plate. That was 3/4" plate welded single pass with a huge wire and high amps. If that didn't kill it, nothing would.