[bug] Handle deleted Part (#12578) (#12586)

(cherry picked from commit 28fea388f6)

Co-authored-by: Oliver <oliver.henry.walters@gmail.com>

src/backend/InvenTree/part/models.py

@@ -2957,7 +2957,9 @@ class PartPricing(common.models.MetaMixin):
             try:
                 self.refresh_from_db()
             except PartPricing.DoesNotExist:
-                pass
+                # The underlying Part (and this pricing entry) has been deleted
+                # since this update was scheduled - nothing to do
+                return
 
         self.update_bom_cost(save=False)
         self.update_purchase_cost(save=False)