As pointed out by Andrew in https://tracker.moodle.org/browse/MDL-51075?focusedCommentId=393487&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-393487, filter glossary is the proud host of one of our JS memory leaks.

To reproduce:

1. Add a mod_page instance with a big text containing a glossary entry concept (autolinked) multiple times
2. Go to the mod_page page
3. Open timeline chrome dev tools tab and start recording
4. Open and close the glossary concept JS popup a few times, you can try forcing garbage collection after closing a popup so we are sure that all memory that will be freed is freed
5. Stop recording and see how JS, nodes and listeners has been going up for each alertpanel that was opened.