STG error page for Firefox View virtual tab at startup

[Terrance]

Describe the bug

At startup, I often get an "Unsupported URL" duplicate about:firefoxview tab.

Note that Firefox View isn't a tab in the usual sense -- it's a screen accessible from a toolbar button that defaults to the far left of pinned tabs, and isn't part of Ctrl-Tab cycling.

To reproduce

0. Ensure Firefox View is enabled (right-click UI > Customise Toolbar... and add the button if missing).
1. Restart Firefox.
2. Find duplicate about:firefoxview tab among restored tabs.

Screenshots

(the real Firefox View is the Firefox icon in the top-left)

Desktop

• OS and version: Windows 10 22H2 (19045.3208)
• Firefox version: 116.0b8
• Simple Tab Groups version: 5.2

[FM33]

Same here. Fx 128 / Ubuntu 24.04 / STG 5.2