Steps to reproduce:
setup an XWiki on any of the supported databases (I tested on MySQL and Oracle) (XE or XEM)
skip the Distribution Wizard
import the XAR manually
Application Panel is empty
Check the stacktrace from comment
WORKAROUND: restarting the wiki will make the Application Panel look good.
I not sure if this is a blocker anymore, since there is an easy workaround. It certainly needs to be fixed.