A delisted short stock position will remain in your account until either the stock starts trading again or until the time the DTC removes the shares from your account. It is unknown how long it will take for the company to dissolve and for the DTC to remove the shares.
For additional information, please see the Finra Investor Alert titled "When Trading Stops: What You Need to Know About Halts, Suspensions and Other Interruptions" and the MEXEM Knowledge Base.