Integrity Checker Spam Logs with Warning Messages

Since the changes on 6.1 with pkey for issues. Therefore running the Integrity checker spams the logs with the following WARN messages.

2013-11-14 15:57:31,047 http-bio-8080-exec-20 WARN admin 957x171x1 1m88p5t 10.60.2.155,10.60.2.155 /secure/admin/IntegrityChecker.jspa [atlassian.jira.ofbiz.IssueGenericValue] Issue (id=null) has empty field 'num'. Returning null for 'key'.

For customers that have more than 50 thousands issues, the warning appears more than 50 thousands time when running integrity checker.

Steps to Reproduce

1. On JIRA 6.1 onwards, create issue
2. Run Integrity Checker