bug#43837: 28.0.50; [NS] Internal border of inactive frame loses color

[Andrii Kolomoiets]

In 'emacs -Q':

1. M-: (setq test-frame (make-frame '((left . 50) (top . 50))))
2. C-x 5 o
3. M-: (set-face-background 'internal-border "blue" test-frame)
4. M-: (modify-frame-parameters test-frame '((background-color . "black")))

Now (face-background 'internal-border test-frame) returns nil.
If we skip step 2, then the internal border color remains.


In GNU Emacs 28.0.50 (build 2, x86_64-apple-darwin19.6.0, NS appkit-1894.60 
Version 10.15.6 (Build 19G2021))
Windowing system distributor 'Apple', version 10.3.1894
System Description:  Mac OS X 10.15.6