Sidebar widget: wrong color in the dropdown menu entry

<img width="310" height="139" alt="Image" src="https://github.com/user-attachments/assets/b488c317-52b0-4450-9bbb-70d4aa7b6a0b" />

Reported here: https://community.humhub.com/comment/perma?id=54941

Tested on latest 1.18.0, I confirm the issue