When altering "Coordinate Light Map Index" in a static mesh when "Generate Lightmap UVs" is enabled in LOD 0 the engine will crash or "Coordinate Light Map Index" will be set to 0.

A demonstration can been seen [Link Removed].

Found in 4.24.1 CL#10757647
Reproduced in 4.25 Main CL#10872318

Steps to Reproduce

1. Make a copy of the Cube mesh in the content browser.
2. Open the copied cube static Mesh.
3. Disable, then re-enable "Generate Lightmap UVs" in LOD 0.
4. In LOD Settings change "Number of LODs" to a number greater than 1 and select "Apply Changes".
5. Attempt to set "Light Map Coordinate Index" to a number greater than 1. IMPORTANT: You need to submit the change using the Enter key, simply changing focus won't reproduce the bug.

Result: Light Map Coordinate Index will be set to 0 or the engine will crash.

Expected: Light Map Coordinate Index will be set to 1.

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Affects Versions4.
Target Fix4.25
Fix Commit10899325
Main Commit11224363
CreatedDec 31, 2019
ResolvedJan 7, 2020
UpdatedFeb 11, 2020