New Identity is busted with the update to Nightly 06/22/2021

After updating my nightly to the one for 06/22/2021 the New Identity functionality is busted:

[06-22 06:43:49] Torbutton INFO: New Identity: Disabling JS
[06-22 06:43:49] Torbutton VERB: Toggle window plugins
[06-22 06:43:49] Torbutton WARN: DocShell is null for: about:tor
[06-22 06:43:49] Torbutton INFO: New Identity: Closing tabs and clearing searchbox
[06-22 06:43:49] Torbutton INFO: Closing tabs...
[06-22 06:43:49] Torbutton INFO: Tab count for window: 1
[06-22 06:43:49] Torbutton DBUG: Closing windows...
[06-22 06:43:49] Torbutton INFO: Closed all tabs
[06-22 06:43:49] Torbutton INFO: New Identity: Emitting Private Browsing Session clear event
Exiting due to channel error.
Exiting due to channel error.
Jun 22 06:43:49.000 [notice] Owning controller connection has closed -- exiting now.
Jun 22 06:43:49.000 [notice] Catching signal TERM, exiting cleanly.
Exiting due to channel error.

And my Tor Browser is essentially shut down.

I suspect this is related to #40475 (closed) (which is why I am filing this ticket in this project) as I am pretty sure New Identity worked yesterday. (Might be worth double-checking, though)