Mail Handler isn't creating new user

Issue Summary

New users isn't created when email sent from non-existing user using the "create user" option checkbox within the mail handler configuration.

Steps to Reproduce

1. Go to JIRA > JIRA Settings > System > Incoming Mail or "GG" Incoming Mail
2. Click "Add incoming mail handler" button to create new mail handler.
3. Click Next
4. Select "Create a new issue or add acomment"
5. Tick "Create Users" checkbox
6. Click Add

Expected Results

Create new JIRA user and issue using the user's email as a username, subject and content.

Actual Results

User and issue isn't created

Workaround

To allow Jira to handle email messages sent from people without a Jira user account:

1. Create an anonymous or dummy mail account on your mail server.
2. Create an equivalent anonymous or dummy Jira user account, whose email address matches the mail account you just created.
3. When configuring your mail handler options, set the Default Reporter to be the anonymous or dummy Jira user account.