[FIX] stock: _log_less_quantities_than_expected call...

[FIX] stock: _log_less_quantities_than_expected call _log_activity_get_documents with empty dict and raises error

closes odoo/odoo#121570

Signed-off-by: Tiffany Chang <tic@odoo.com>

addons/stock/wizard/stock_backorder_confirmation.py

@@ -45,7 +45,8 @@ class StockBackorderConfirmation(models.TransientModel):
                                  move.quantity_done,
                                  precision_rounding=move.product_uom.rounding) > 0:
                     moves_to_log[move] = (move.quantity_done, move.product_uom_qty)
-            pick_id._log_less_quantities_than_expected(moves_to_log)
+            if moves_to_log:
+                pick_id._log_less_quantities_than_expected(moves_to_log)
 
     def process(self):
         pickings_to_do = self.env['stock.picking']