No it is not technically void. You will likely continue to owe the money until you pay it.

I would have to verify it but typically an employer cannot withhold anything from your pay (other than the statutory withholdings or that a court orders (garishment would fall under this)) unless you authorize the withholding. That means your future employer cannot withhold money from your pay to forward to the current employer unless you authoriize it. So, just don’t authorize the withholding.

Your current employer can sue you and presumably obtain a judgment against you. It doesn’t sound like your wages can be garnished for the resulting judgment.

Your current employer can take all other lawful actions to collect on the judgment though. It will also show up on your credit report as well. That will screw with obtaining credit and it could screw with your employment.