Old Content Notifier job throws exception when ran manually

When the 'Old Content Notifier' job is ran manually via the 'Run Now' button, an exception will be thrown and the script will not run. To reproduce:

1. Set up a mail server
2. Create old content (the Demonstration Space that is set up when you build Confluence for the first time will suffice)
3. Run the 'Old Content Notifier' job (you need to type in a CQL query that will match the old content):

This error does not occur when the job is added to be ran on a schedule. The job works as expected. This only happens using the "Run now" button.