Delete does nothing on an in-use Custom Attribute when re-triggered after cancelling the deletion confirmation prompt in the VFX Graph Blackboard

Steps to reproduce:

1. Create a URP 3D project with the Visual Effect Graph package installed
2. Create a Visual Effect Graph asset and open it
3. In the Blackboard, add a Custom Attribute and use it in the workspace (e.g. drag it into the graph so a node references it)
4. Right-click the Custom Attribute in the Blackboard and choose Delete
5. In the confirmation prompt, choose No (cancel)
6. Right-click the same Custom Attribute again and choose Delete

Actual results:

The second Delete does nothing, no confirmation prompt appears and the attribute is
not removed. Delete only becomes responsive again after deselecting and reselecting
the attribute (which then shows the prompt as expected).

Expected results:

Cancelling the confirmation leaves the attribute selected and the Delete command
immediately usable, choosing Delete again shows the confirmation prompt as normal.

Reproducible with versions: 6000.0.0f1, 6000.0.77f1, 6000.3.16f1, 6000.4.12f1, 6000.5.0f1, 6000.6.0a7

Tested on (OS): Windows 11