JS toggle of meeting contents is broken.

Clicking on a meeting item to unfold its content raises a JS exception on Teamraum 4.1c (Plone 4.3.1)

    [buildout]
    extends = 
        http://dist.plone.org/release/4.3.1/versions.cfg
        http://kgs.4teamwork.ch/release/teamraum/4.1rc