Nested level visibility track bug

The Level Visibility tracks part of a Subsequence are turned off every time you save the Leve Sequence.
It does not happen if Level Visibility tracks are added in the main Sequence.

1. Download the Licensee's test project and open (see addl info URL)
2. Open the Level “/Game/Developers/hchuang/Collections/test_bugs/test_P.umap”
3. Open the Level Sequence “/Game/Developers/hchuang/Collections/test_bugs/LS_test.uasset”
4. Observe both Sublevels “sub_lgts” and “sub_shapes” are part of the Level Visibility track, set to Visible and visible in Viewport.
5. Open the Level Sequence “/Game/Developers/hchuang/Collections/test_bugs/cam_01.uasset”
6. Observe that “LS_Test” is a Subsequence of “cam_01” and all objects are still visible in the Viewport.
7. In Sequencer click on the “Save the current sequence and any subsequences” icon.
8. Observe that all Sublevels visibility is turned off.