Closes #39318 The rules panel on the rules library window was rendering a black background when the `panel.background` property on the active theme had some level of transparency (for example `1917264D` on `nightfox` theme). <img width="1650" height="889" alt="image" src="https://github.com/user-attachments/assets/6a8d124a-38da-4d01-817a-c289926bd39c" /> Left is before, right is after. The bug can be replicated by using `theme_overrides` on settings: ```json "experimental.theme_overrides": { "panel.background": "#00000000", "background": "#ffffff" }, ``` Release Notes: - Fix "secondary" background on rules panel