Child issues not displayed in WBS Gantt-Chart after a version is deleted?

Summary

After a version is deleted, child issues are not displayed in WBS Gantt-Chart.

Workaround

This behavior is caused by the following bug: https://jira.atlassian.com/browse/JRA-22351
To fix this, execute the SQL below:

delete from nodeassociation where source_node_entity = 'Issue' and sink_node_entity = 'Version' and sink_node_id not in (select id from projectversion);