Right around this point in Engine/Private/SkeletalMeshMerge.cpp https://github.com/EpicGames/UnrealEngine/blob/c3caf7b6bf12ae4c8e09b606f10a09776b4d1f38/Engine/Source/Runtime/Engine/Private/SkeletalMeshMerge.cpp#L60
checkf(false, TEXT("Invalid number of UV sets. Must be between 0 and 4") );\
However, the switch immediately above it only has cases for 1,2,3,4, it does not include 0.
What is the correct behavior for 0? Should it be processed same as 1-4, differently from 1-4, or should it be an error and the error message updated to say 1-4?