Animation Add Property modal is empty and still opens a modal full of whitespace when all the Properties are already added

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Create a new Cube GameObject (GameObject > 3D Object > Cube)
3. Select the newly added Cube GameObject in the Hierarchy window
4. Open the Animation window (Window > Animation > Animation)
5. Create a new Animation
6. Click the "Add Property" button and add all the properties
7. Click the "Add Property" button again
8. Observe the opened modal

Actual results: The opened "Add Property" modal is completely empty

Expected results: Either the "Add Property" button is greyed out/inactive or some other solution instead of opening a modal that is completely empty

Reproducible with versions: 6000.0.69f1, 6000.3.10f1, 6000.4.0b11, 6000.5.0a8

Tested on (OS): MacOS Silicon Tahoe 26.2, Ubuntu 24.04