Error in new version: cannot read property "indexOf" of undefined

Sorry to bug you guys again. Since I updated the plugin, the non-highlander expand stopped working:

http://blogs.getty.edu/ clone /testing-default-audio-post-see-what-happens/

“Transcript” is supposed to expand.

I’m getting this error in the console:
collapse.js?ver=1.6.4:353 Uncaught TypeError: Cannot read property ‘indexOf’ of undefined

https://wordpress.org/plugins/jquery-collapse-o-matic/