[FIX] delivery: weight computation without quant

The weight computation was not working anymore on packages that don't
have any quant, because they are fresh ones.

We fix this by setting back the behaviour with the picking id in
context and adapt the function to find the corresponding move lines.

closes odoo/odoo#30071

addons/delivery/models/stock_picking.py

@@ -16,8 +16,13 @@ class StockQuantPackage(models.Model):
     @api.depends('quant_ids')
     def _compute_weight(self):
         weight = 0.0
-        for quant in self.quant_ids:
-            weight += quant.quantity * quant.product_id.weight
+        if self.env.context.get('picking_id'):
+            current_picking_move_line_ids = self.env['stock.move.line'].search([('result_package_id', '=', self.id), ('picking_id', '=', self.env.context['picking_id'])])
+            for ml in current_picking_move_line_ids:
+                weight += ml.product_uom_id._compute_quantity(ml.qty_done,ml.product_id.uom_id) * ml.product_id.weight
+        else:
+            for quant in self.quant_ids:
+                weight += quant.quantity * quant.product_id.weight
         self.weight = weight
 
     weight = fields.Float(compute='_compute_weight', help="Weight computed based on the sum of the weights of the products.")