Fix crash if Bundle.designated_price is set to null

src/pretix/control/forms/item.py

@@ -1,3 +1,5 @@
+from decimal import Decimal
+
 from django import forms
 from django.core.exceptions import ValidationError
 from django.db.models import Max
@@ -687,6 +689,10 @@ class ItemBundleForm(I18nModelForm):
 
     def clean(self):
         d = super().clean()
+        if not self.cleaned_data['designated_price']:
+            d['designated_price'] = Decimal('0.00')
+            self.instance.designated_price = Decimal('0.00')
+
         if 'itemvar' in self.cleaned_data:
             if '-' in self.cleaned_data['itemvar']:
                 itemid, varid = self.cleaned_data['itemvar'].split('-')

src/tests/control/test_items.py

@@ -500,12 +500,13 @@ class ItemsTest(ItemFormTest):
             'bundles-0-id': '',
             'bundles-0-itemvar': str(self.item1.pk),
             'bundles-0-count': '2',
-            'bundles-0-designated_price': '2.00',
+            'bundles-0-designated_price': '',
         })
         self.client.post('/control/event/%s/%s/items/%d/' % (self.orga1.slug, self.event1.slug, self.item2.id), d)
         with scopes_disabled():
             assert self.item2.bundles.exists()
             assert self.item2.bundles.first().bundled_item == self.item1
+            assert self.item2.bundles.first().designated_price == Decimal('0.000')
         d.update({
             'bundles-TOTAL_FORMS': '1',
             'bundles-INITIAL_FORMS': '1',