On selecting a dropdown icon or its name, Nodes and properties don't expand or collapse in the VFX Graph, refer the attached video

Steps to Repro:
1. Open a new Project with HDRP Template
2. Project > Created > Visual Effects > Visual Effect Graph
3. Focus on Spawn System
4. Try to expand Nodes and Properties on clicking arrow dropdown icon

Actual Result:
Properties and Nodes don't expand and collapse on selecting the arrow dropdown icon

Expected Result:
Properties and Nodes are expanded and collapsed gracefully

Reproducible on:
2020.2.0a16 with package version 9.0.0-preview.13, 8.1.0

Working fine on:
2020.2.0a15, 2020.1.0b14 with package version 9.0.0-preview.13, 8.1.0

Environment:
Windows 10 and Mac 10.15