Open groupchats toggle emits an error

[linkmauve]

Describe the bug
The toggle label “open bookmarks” emits Uncaught TypeError: can't access property "querySelector", this.el is undefined and then doesn’t do anything else.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://inverse.chat
2. Click on “open bookmarks” in the left pane.
3. See error

Expected behavior
All open rooms would be hidden, the triangle would change direction, and no traceback would be displayed. Then when clicking it again, it would go back as it was originally.

Screenshots
N/A

Environment (please complete the following information):

• Desktop
• Firefox (Nightly from the 2021-09-04)
• Converse.js version 8.0

Additional context
N/A

[jcbrand]

I see this with the 'Open groupchats' list, not the bookmarks.