[FIX] mrp: remove workorder_ids on removing bom_id

Method `_onchange_workorder_ids` will create workorder_ids
for the the selected bom but it was not re-setting it on removing
BoM.
It was causing issue on `_action_confirm` as Bom for the selected
WO will not be found.

closes odoo/odoo#69662

Fixes: #68261
X-original-commit: 13832912daafad7c472d7414eaacede9e302e787
Signed-off-by: Rémy Voet <ryv-odoo@users.noreply.github.com>

addons/mrp/models/mrp_production.py

@@ -671,6 +671,8 @@ class MrpProduction(models.Model):
     def _onchange_workorder_ids(self):
         if self.bom_id:
             self._create_workorder()
+        else:
+            self.workorder_ids = False
 
     def write(self, vals):
         if 'workorder_ids' in self: