tests: don't let logged error test send out emails (#17089)

tests/test_backoffice_pages.py

@@ -3493,6 +3493,9 @@ def test_backoffice_logged_errors(pub):
     resp = resp.click('Delete').follow()
     assert LoggedError.count() == 0
 
+    pub.cfg.update({'debug': {'error_email': None}})
+    pub.write_cfg()
+
     app = get_app(pub)
     resp = app.get('/test/')
     resp = resp.form.submit('submit').follow()