db: permission sync generates a warning if there are no updated permissions

Created by: LawnGnome

I have no idea how my local database ended up in a state where this could be triggered, but SetRepoPendingPermissions() has an issue where it causes a warning to be generated if there are no updated permissions to store.

Basically, if this loop doesn't append any values to updatedPerms, one ends up building a query in updateUserPendingPermissionsBatchQuery() that looks like this:

-- source: enterprise/internal/db/perms_store.go:updateUserPendingPermissionsBatchQuery
UPDATE user_pending_permissions
SET
	object_ids_ints = update.object_ids_ints,
	updated_at = update.updated_at
FROM (VALUES ) AS update (id, object_ids_ints, updated_at)
WHERE user_pending_permissions.id = update.id

Note the empty space after VALUES where the processed updatedPerms would be interpolated in, were there any.

I don't think there's any real user impact here, but the warnings are unsightly and annoying.