forms: display an empty string if there's no handling role (#20633)

tests/test_form_pages.py

@@ -388,6 +388,7 @@ def test_form_submit(pub):
     assert next_page.status_int == 302
     next_page = next_page.follow()
     assert 'The form has been recorded' in next_page.body
+    assert not 'None' in next_page.body
     assert formdef.data_class().count() == 1
 
 def test_form_submit_no_confirmation(pub):

wcs/forms/common.py

@@ -193,7 +193,7 @@ class FormStatusPage(Directory):
     def get_handling_role_info_text(self):
         handling_role = self.filled.get_handling_role()
         if not (handling_role and handling_role.details):
-            return None
+            return ''
         r = TemplateIO(html=True)
         endpoint_status = self.formdef.workflow.get_endpoint_status()
         r += htmltext('<p>')