VisualReferenceElement object field has an icon displayed on a null reference by default

Steps to reproduce:

1. Create a new project
2. Create and instantiate a new script in the Hierarchy
   1. Inside the script, declare a public VisualElementReference object
3. Save and focus on the Editor
4. Observe the VisualElementReference field in the Inspector

Actual results: A VisualElement icon is seen on a null reference by default

Expected results: No icon is seen on a null reference

Reproducible with versions: 6000.5.0a5, 6000.5.0b8, 6000.6.0a5

Can’t test with versions: 6000.0.75f1, 6000.3.15f1, 6000.4.7f1, 6000.5.0a3 (No VisualElementReference class)

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

Notes: 

• The Icon changes based on the selected reference, but the VisualElement icon is the default
• Inconsistent compared to other object reference fields in the Editor