Issue Summary

Switching from "Exemptions" tab to "List of limited accounts" tab in Rate limiting admin page causes page to go blank when a user in the Exemptions tab has not been rate limited in the past

This is reproducible on Data Center: yes

Steps to Reproduce

1. Add a user to the exemption list that has not been rate limited - example user "anonymous"
2. switch to the "List of limited accounts" tab

Expected Results

The "List of limited accounts" tab loads a list of users that has been limited

Actual Results

The Rate Limit page goes blank:

The below exception is thrown in the browser console:

Workaround

Refresh the page