backoffice: fix fields page when a field label is None (#51728)

tests/admin_pages/test_form.py

@@ -1169,6 +1169,19 @@ def test_form_new_field(pub):
     assert '<h3 data-field-id="1">baz</h3>' in resp.text
 
 
+def test_form_field_without_label(pub):
+    create_superuser(pub)
+
+    FormDef.wipe()
+    formdef = FormDef()
+    formdef.name = 'form title'
+    formdef.fields = [fields.CommentField(id='1', label=None, type='comment')]
+    formdef.store()
+
+    app = login(get_app(pub))
+    app.get('/backoffice/forms/1/fields/', status=200)  # ok, no error
+
+
 def test_form_delete_field(pub):
     create_superuser(pub)
     create_role()

tests/test_fields.py

@@ -282,7 +282,7 @@ def test_comment():
     form = Form(use_tokens=False)
     field.add_to_form(form)
     assert re.match(  # regex to handle different beautifulsoup behaviours
-        '<div class="comment-field\s?">\n<p>Foo</p>\n<p>Bar</p>\n<p>Baz</p>\n</div>',
+        r'<div class="comment-field\s?">\n<p>Foo</p>\n<p>Bar</p>\n<p>Baz</p>\n</div>',
         str(BeautifulSoup(str(form.render())).find('div')),
     )
 

wcs/fields.py

@@ -253,7 +253,7 @@ class Field(object):
 
     @property
     def unhtmled_label(self):
-        return force_str(html.unescape(force_text(re.sub('<.*?>', ' ', self.label))).strip())
+        return force_str(html.unescape(force_text(re.sub('<.*?>', ' ', self.label or ''))).strip())
 
     def get_admin_attributes(self):
         return ['label', 'type', 'condition']