URL in popups begin from the tab bar instead of the main window

[silverwings15]

Hiya, this happens when i enable "show URL in popup".

Pale Moon 28.1.0, TK2 0.13.3, Windows 10 x64

edit: seems that the browser isn't being told that the tab bar is its own zone. another extension of mine, Tab Scope, has the same interaction with the tab bar

this is how it should work:

this is how it currently is in TK2: