Model preview arrows do nothing when no additional preview images are available in AI model selection

Steps to reproduce:

1. Create a Unity project
2. Click the "AI" button
3. Click "Agree and install Unity AI"
4. Go to AI > Generate New > Cubemap
5. In the left-hand panel, select "Change" to change model
6. Hover over the available models
7. Observe arrows appear for changing the preview/thumbnail
8. Click on the arrows

Actual results: Model preview image does not change, likely due to no additional images being available

Expected results: Either the model preview image changes to another image when clicking the arrows, or the arrows are not shown/are disabled when no additional preview images are available

Reproducible with versions: 1.6.0-pre.1, 2.1.0-pre.1 (6000.4.0b11, 6000.5.0a8)

Tested on (OS): Windows 11

Notes:

• This is also reproducible in the 3D Model Generator models and any other models that dont have images