Batch download queue not cleared upon packed QWK packet

Before the "new filebase" merge of 2021, a user's batch download queue would be cleared when a QWK packet was successfully packed for them via the event thread (i.e. triggered via semaphore file). That was lost in the new filebase change (the batch download queue would not be cleared) - caught by Coverity (CID 350336).

It appears pre-packed QWK packets never cleared the batch download queue (does anyone actually use this feature in this day and age?) - fixed.