Merge branch 'Qwann/SmallFixes' into 'master'

Activity parent nullable

- Fix db error if an activity doesn't have a parent (activity template).

See merge request !18

event/models.py

@@ -167,6 +167,7 @@ class Activity(AbstractActivityTemplate):
                     ActivityTemplate,
                     related_name="children",
                     blank=True,
+                    null=True,
                 )
     staff = models.ManyToManyField(
                     User,