Improve the handling of the "Unable to resolve an issue with key: xxx-nnnn" error

Summary

There can be a significant number of the below errors in JIRA logs which is causing customers to raise issues and be more concerned about their instance that need be:

2013-04-17 23:15:19,474 Sending mailitem com.atlassian.jira.mail.IssueMailQueueItem@6bce2c0c[issue=com.atlassian.jira.issue.IssueImpl@b185a44[id=312164,summary=why is iron man such a badass?,key=AVG-5269,created=2013-04-12 09:31:03.0,updated=2013-04-17 23:14:18.834,assignee=captain.planet:1,reporter=defaultavenger:1],remoteUser=admin:1,notificationType=All_Watchers,eventTypeId=6,templateId=6] INFO ServiceRunner    Mail Queue Service [renderer.wiki.links.JiraIssueLink] Unable to resolve an issue with key: AVG-5269

Environment

• Google SMTP.
• PostgreSQL 9.1.

Steps to Reproduce

1. Admin comments on issue JRA-123 with body "Hey Fred I think you should take a look at JRA-55567!"
2. When the e-mail tries render the wiki markup, it doesn't have a reference to any "current user", and permission checks in JiraIssueLink which is called during wiki rendering are done as Anonymous. Anonymous doesn't have permission to see JRA-55567 (lets say) which throws the ParseException which results in the error being logged
3. Shouldn't cause any problems other than the issue not being linked but being plaintext in the e-mail body I think

Or

Add "UTF-8" to a comment, and it will try to render it as an issue link.

Expected Results

No error is present in the logs.

Actual Results

We see this error.

Notes

This is thrown by JiraIssueLink.java due to a ParseException. Essentially this is a completely harmless error and can be ignored.