[Bug] Broken compatibility with Hide Caption Titlebar Plus since version 1.4.7

[Baguettedood]

OS: Windows 10 x64 (Version 1511) Firefox version: 48.0.2 Bug introduced in: Tab Tree 1.4.7 (Also present in 1.4.8) Last known working version: Tab Tree 1.4.6.

1. Install Hide Caption Titlebar Plus (version 3.0.10). Configuration used, though it shouldn't matter: http://imgur.com/a/gc7Rl
2. Install Tab Tree (version 1.4.8).
3. Restart Firefox. The first window will look normal, with the smaller titlebar.
4. Create a second window. The second window will have the system titlebar. Example of behavior: http://imgur.com/a/9yx9C

Downgrading Tab Tree to 1.4.6 fixes the issue. Other things of note:

• Disabling and re-enablling Hide Caption Titlebar Plus returns the titlebars to their expected state.
• I wasn't sure whether to post this on this bugtracker or Hide Caption Titlebar Plus', but the issue seems to arise from an update here.
• Happens in windowed and maximized modes.