[FIX] stock_picking_batch: remove empty pickings

If a picking is totally empty (no move line with quantity recorded) in a
batch at validation. This one will be ignored by the immediate transfer
mechanism as well as the backorder creation. It is simply remove from
the batch.

closes odoo/odoo#63291

Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>