Unhandled exception in Sweep Loop when updating parameters on multiple sweep loops at the same time

Environment:

Windows 10, 64-bit

OpenTAP 9.4.1

Steps to reproduce:

1. Add two Sweep Loops each with a Dialog
2. Select both steps
3. Open Sweep parameter dropdown and make a selection

Actual result:

Exception: Value cannot be null.Parameter name: source at System.Linq.Enumerable.FirstOrDefaultTSource

Log: SessionLog_2020-02-14_17-16-29.txt

Expected result:

Other remarks: