Work Tree: Theme Groups do not show up if Portfolio/Solution/Program is selected in Tier 1 and no PI is selected in Tier 2

Issue Summary

If there is no PI selected on TIer 2, Theme groups are not displayed at all.

Steps to Reproduce

1. Go to Work Tree
2. Select Portfolio 1/Solution 1/Program 1 in Tier 1.
3. Go to the Work Tree - Theme Group view.
4. Do not select any Release in Tier 2.

Expected Results

All Theme Groups assigned to Portfolio/Solution/Program should show up:

if Portfolio 1/Solution 1 are selected in Tier 1 - Theme Groups 1-2 should be shown;
if Program 1 is selected in Tier 1 - Theme Group 1 should be shown.

Actual Results

No Theme Groups show up on the page.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available