CMS fails to log me in after upgrade from 7.9.1 to 7.9.3

Hi Hippo-ers,

After upgrading our production environment to hippo 7.9.3 (from 7.9.1) we ran into a problem when loggin in to the cms. It complains about a missing wicket component: Unable to find component with id 'extension.logout' also see attached log-file.

We reverted de cms version to 7.9.1 again now we can login again. Does anybody have a clue how to fix this?

hippo version: 7.9.3
java version: 1.7.0_67