Show user warning if "add item to custorder" fails

specifically, if user enters alpha chars for cost/price fields

tailbone/templates/custorders/create.mako

@@ -2124,6 +2124,8 @@
 
                     this.itemDialogSaving = false
                     this.showingItemDialog = false
+                }, response => {
+                    this.itemDialogSaving = false
                 })
             },
         },

tailbone/views/custorders/orders.py

@@ -864,7 +864,10 @@ class CustomerOrderView(MasterView):
 
             for field in ('unit_cost', 'regular_price_amount', 'case_size'):
                 if field in pending_info:
+                    try:
                         pending_info[field] = decimal.Decimal(pending_info[field])
+                    except decimal.InvalidOperation:
+                        return {'error': f"Invalid entry for field: {field}"}
 
             pending_info['user'] = self.request.user