When you go to the Issue search/issue navigator, it appears to be completely broken. There's no way to search. The only buttons available are "Share", "Export", and "Tools" and they don't do anything when clicked.

Other strange problems may also crop up, this occurs if JIRA Service Desk isn't licensed, as it causes problems with rendering some of the javascript used within JIRA. If you're seeing strange behaviour please try the workaround below.

Workaround
Go to the Manage add-ons page and disable the JIRA Service Desk plugin.