[BUG] custom CSS is only applied after restart

[mydeveloperplanet]

DevoxxGenie v0.6.2

1. Enable Dark mode
2. Enable custom CSS and click Apply
3. Prompt a question, the custom CSS is not applied
4. restart the IDE
5. Prompt a question, now the custom CSS is applied (after fixing [ENHANCEMENT] Default Dark Theme colors in conversation are too light #682 )