Event creation: call plugin installed() after persisting event (#2133)

With #2089, PluginConfig.installed() is also called for newly created events.
However, the passed event argument is still not committed. The plugins
cannot use the event to insert or select objects, as it does not have an
ID yet.

src/pretix/control/views/main.py

@@ -262,10 +262,10 @@ class EventWizard(SafeSessionWizardView):
         with transaction.atomic(), language(basics_data['locale']):
             event = form_dict['basics'].instance
             event.organizer = foundation_data['organizer']
-            event.set_active_plugins(settings.PRETIX_PLUGINS_DEFAULT.split(","), allow_restricted=True)
             event.has_subevents = foundation_data['has_subevents']
             event.testmode = True
             form_dict['basics'].save()
+            event.set_active_plugins(settings.PRETIX_PLUGINS_DEFAULT.split(","), allow_restricted=True)
             event.log_action(
                 'pretix.event.added',
                 user=self.request.user,