Opening file failed popup appears on duplicating probes and creating a prefab of Light Probe Group.

Steps to Reproduce:
1. Create a new Project.
2. Hierarchy > Create > Light > Light Probe Group
3. Edit Light Probes > Select All > Duplicate Selected
4 Create a prefab of Light Probe Group

Actual Result:
Opening file failed popup appears and windows and Editor keeps flickering on MacOS.

Expected Result:
Prefab created gracefully.

Reproducible on:
2019.3.0a3, 2019.2.0b3, 2019.2.0a12

Not Reproducible on:
2019.2.0a11

Environment:
Windows and MacOS