“NullReferenceException” error thrown when adding element to “Output Slots” in Debug Inspector for Update Particle Block

Steps to reproduce:
1. Create new Unity project using Universal 3D Template
2. Open Package Manager window and install Visual Effects Graph
3. Create VFX Graph Asset using “Firework” Template (From Create new VFX Asset window)
4. Open created VFX Asset
5. Select any Update Particle Block
6. In Inspector window switch to Debug mode (click on kebab button > Debug)
7. Expand “Output Slots” and press “+” to add element to the list
8. Observe the Console window

Actual results: “NullReferenceException” error is thrown in the Console when adding an element to Output Slots in Debug Inspector

Expected results: The operation should be safely handled without throwing errors, ff Output Slots are not intended to be user-editable, the field should be read‑only in Debug mode

Reproducible with versions: 6000.0.76f1, 6000.3.16f1, 6000.4.9f1, 6000.5.0b10, 6000.6.0a6

Tested on (OS): macOS Tahoe 26.4.1