Inconsistent Red X icons when using World Composition

This issue takes a few attempts to repro. Sometimes when saving the icons will remain normal, but other times a red X will be displayed instead. Opening up the Level that is displaying the X and re=saving it sometimes causes it to go away. If another sublevel is added it can reappear. This issue was not present in 4.19.2 (CL-4033788) and is a regression.

This was reported and tested in 4.20.3 (CL-4369336). This was reproduced in Main 4.21 (CL-4378440)

1. Open the UE4 Editor and create a Blank project
2. In the Content folder, create a few Levels
3. Select one to be your main Level and enable World Composition on it
4. Load up all the sublevels and click Save All

Results: Instead of the normal Save icon, a red X icon is sometimes displayed

Expected: The normal Save icon is there