Loading Requests with Anonymous Comments in the Customer Portal fails with 500 error NullPointerException

Summary

Loading a Service Desk Request through the Customer Portal fails with a NullPointerException, which is displayed as an XML file:
500error.xml

Steps to Reproduce

1. Create a project;
2. Create an issue in this project;
3. Grant Anonymous access and permission to comment on this project;
4. As an anonymous user, add a comment to this ticket.
5. Install JIRA Service Desk;
6. Create a Service Desk from this project;
7. Try to access this issue from the Customer Portal.

Expected Results

The customer would be able to access the issue with no problem.

Actual Results

The user is unable to open the request, and an XML file is displayed instead: 500error.xml
The following is displayed in the atlassian-jira.log file and the complete stack trace can be found in complete_stack_trace.txt .

Failed to get event initiating user to set issue property 'request.public-activity.lastupdated'

Workaround

• Upgrade to JIRA Service Desk 2.3.5+.
• Or delete the offending comment and re-add it as a JIRA user.