-Editor crashes on assigning "New VFX Subgraph Block" to "Empty Subgraph Block" node from asset selector window.
-No crash report generated.

Steps to repro:
1. Create a new HDRP template project.
2. Project Window > Click "+" > Visual Effects > Visual Effect Subgraph Block.
3. Open Subgraph Block > Select Block Subgraph node.
4. Press Space bar > Subgraph Block > Empty Subgraph Block.
5. Select Empty Subgraph Block > Inspector > Assign New VFX Subgraph Block.

Actual Result:
Editor crashes on assigning "New VFX Subgraph Block".

Expected Result:
"New VFX Subgraph Block" assigned to "Empty Subgraph Block" node from asset selector window.

Reproducible in:
2020.2.0a13, 2020.1.0b11, 2019.3.15f1, 2019.3.2f1 with Package version 9.0.0, 8.1.0, 8.0.1, 7.3.1.

Environment:
Occurring only on Windows 10.