White rectangle when disabling `Calendar`

### Bug explanation

When setting `IsEnabled="False"` on a `Calendar`, a white rectangle is shown:

<img width="834" height="681" alt="Image" src="https://github.com/user-attachments/assets/a6a79b47-4cb5-488e-bead-506ad846d471" />

The red border is due to Snoop, ignore that 😄 

### Version

latest main (5.3.0-ci1132)