tests/admin_pages/test_form.py

@@ -263,6 +263,14 @@ def test_forms_edit_management(pub, formdef):
     resp = resp.forms[0].submit().follow()
     assert FormDef.get(1).management_sidebar_items == {'__default__'}
 
+    # unselect all
+    resp = resp.click('Management', href='options/management')
+    for field in resp.forms[0].fields:
+        if field.startswith('management_sidebar_items$'):
+            resp.forms[0][field].checked = False
+    resp = resp.forms[0].submit().follow()
+    assert FormDef.get(1).management_sidebar_items == set()
+
 
 def test_forms_edit_tracking_code(pub, formdef):
     create_superuser(pub)

wcs/admin/forms.py

@@ -526,7 +526,7 @@ class OptionsDirectory(Directory):
                             continue
                     new_value = widget.parse()
                     if attr == 'management_sidebar_items':
-                        new_value = set(new_value)
+                        new_value = set(new_value or [])
                         if new_value == self.formdef.__class__.management_sidebar_items:
                             new_value = {'__default__'}
                     if attr == 'digest_template':