-Editor crashes on opening VFX graph on deleting property in Blackboard window after resetting the property.
-Expanding/Shrinking Flipbook property in Blackboard window, ArgumentOutOfRangeException errors are thrown continuously in the console and Node name changed to exposedName.

Steps to repro:
1. Create a new HDRP template project.
2. Project Window > Click "+" > Visual Effects > Visual Effect Graph.
3. Open in VFX Graph > Add FlipBook property > Inspector > Reset.
4. Expanding/Shrinking Flipbook property.
5. Delete Flipbook property from Blackboard window.
6. Close VFX Graph > Open again.

Actual Result:
-Editor crashes on opening VFX graph after deleting property in Blackboard window.
-ArgumentOutOfRangeException errors are thrown continuously on Expanding/Shrinking Flipbook property in blackboard window.

Expected Result:
Editor should not crash and no errors in the console.

Reproducible in:
2020.2.0a13, 2020.1.0b11, 2020.1.0a23 with Package version 9.0.0, 8.1.0.

Note:
-In Package version 8.0.1 Reset button is disabled.

Environment:
Occurring on Windows 10 & Mac 10.15.