If Tab Sidebar is enabled Waterfox closes and opens the window when starting. Toggling also does this

[mruncreative]

What happened?

If Tab Sidebar is enabled Waterfox closes and opens the window when starting. Toggling Tab Sidebar also does this.
If Tab Sidebar is not active Waterfox starts normally.
I'm using the Cinnamon Desktop environment on X11.

Reproducible?

• I have checked that this issue cannot be reproduced on Mozilla Firefox.

Version

G6

What platform are you seeing the problem on?

Linux

Relevant log output