Text with Legacy Font Asset is not rendered

Steps to reproduce:

1. Create and open a new project
2. Import the "CalibriBold.ttf" font into the project
3. Open 'Window -> Text -> Font Asset Creator'
4. Assign the imported font to 'Source Font' and press Generate Font Atlas
5. Save the asset
6. Select the asset and change its Atlas Population Mode to "Dynamic"
7. Create and open a new UXML in UI Builder
8. Add a Label to the hierarchy, and expand the "Text" foldout
9. Change the Font type to "Font Asset" and assign the Font Asset to the object field
10. Observe the UI Builder viewport

Actual results: Nothing is rendered

Expected results: "Label" is rendered

Reproducible with versions: 6000.0.0f1, 6000.0.78f1, 6000.3.18f1, 6000.5.2f1, 6000.6.0b1, 6000.7.0a1

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• If an Outline is applied, the text appears to be defined, but it's just not rendered
• Reproducible when the UXML is instantiated in the scene as well