Allow not to ask for invoice addresses on free orders

src/pretix/control/forms/event.py

@@ -621,6 +621,10 @@ class InvoiceSettingsForm(SettingsForm):
         widget=forms.CheckboxInput(attrs={'data-checkbox-dependency': '#id_invoice_address_asked'}),
         required=False
     )
+    invoice_address_not_asked_free = forms.BooleanField(
+        label=_('Do not ask for invoice address if an order is free'),
+        required=False
+    )
     invoice_include_free = forms.BooleanField(
         label=_("Show free products on invoices"),
         help_text=_("Note that invoices will never be generated for orders that contain only free "

src/pretix/control/forms/item.py

@@ -43,6 +43,7 @@ class QuestionForm(I18nModelForm):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.fields['items'].queryset = self.instance.event.items.all()
+        self.fields['items'].required = True
         self.fields['dependency_question'].queryset = self.instance.event.questions.filter(
             type__in=(Question.TYPE_BOOLEAN, Question.TYPE_CHOICE, Question.TYPE_CHOICE_MULTIPLE)
         )