The following error messages are reported in the JIRA log file:
There is a user group missing "name" field in JIRA, which breaks group migration to JIRA 4.3+ version.
1. Back up JIRA data
2. Shutdown JIRA instance
3. Run the below script in JIRA database
update groupbase set groupname='DATA-FIX' where groupname is null
4. Reboot JIRA instance
5. If upgrade is successful, find 'DATA-FIX' group in JIRA, delete or rename it.