Forced Black Background of UI Manager window

This is the 2nd time this happens to me in around 2 months, the first time I don't remember why it happened & while a full reinstallation of everything (models, comfy ,...etc) it was fixed, but it came back again 10 days ago. I have a Black Background of the UI Manager's window, it doesn't follow the main ComfyUi theme, even if I change it to light color:

I opened a launched new ComfyUi without any custom-nodes, the promblem still there,
I tried 3 different Browsers (two of them was MS Edge & another Firefox-based browser) all of them has the same issue of this Black BG,
I tried different old/new versions of comfyui-frontend-package , the problem not solved,
I deleted any cache or already older user settings of mine, still no solution,
I checked (from the Dev Tools of the internet Browser I use) & I saw 2 errors related to UI Manager (it was a bout a 404 not found "user.css" )

This Issue happens since ComfyUi 3.46 , I saw it across v3.50 , 3.52 , 3.56, & now I am on ComfyUi 3.57 . Still No Luck.
I can't solve this issue at all this time.


Reproduce the UI Manager window with the main ComfyUI theme set to light, then inspect the browser DevTools errors, especially the reported 404 for user.css. Compare behavior across the mentioned ComfyUI and comfyui-frontend-package versions; done means the UI Manager background follows the selected theme without the user.css error.

Written by the indexing model from the issue text.