Make parent group field not required.

Closes #103 (closed)

biscuit/core/forms.py

@@ -73,6 +73,10 @@ class EditGroupForm(forms.ModelForm):
         model = Group
         fields = ['name', 'short_name', 'members', 'owners', 'parent_groups']
 
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.fields['parent_groups'].required = False
+
 
 class EditSchoolForm(forms.ModelForm):
     class Meta: