that error is occurring when the existing table is being removed to allow for the creation of the new one. So this sounds like a problem with your database (i.e. it is corrupted).
Assuming you have no items stored in it, simply delete C:\users\username\GDStash\db. If you do have stored items, just renamed it, e.g. to _db. That should get you over the import hump, but your items are then not in the new database, so after you have a functioning DB again, we will have to copy your items over from the old DB.