Regression with RecomputeTangents on SkeletalMeshes in 5.6

Licensee noticed a regression in 5.6 where the non-masked recompute tangents option doesn't work anymore. The option is called "Enabled with no mask" in 5.6 but "All" in 5.5. Under the hood, this seems to map to ESkinVertexColorChannel::None in FSkelMeshRenderSection::RecomputeTangentsVertexMaskChannel, which seems to be misinterpreted by the code in FGPUSkinCache::ProcessEntry as meaning the feature is disabled rather than just the masking being disabled.

Changing the logic from

if (RenderSection.RecomputeTangentsVertexMaskChannel < ESkinVertexColorChannel::None && LodData.MultiSizeIndexContainer.GetIndexBuffer())
{
    BufferBits |= EGPUSkinCacheBufferBits::IntermediateTangents;
}

to

if (LodData.MultiSizeIndexContainer.GetIndexBuffer())
{
    BufferBits |= EGPUSkinCacheBufferBits::IntermediateTangents;
}

makes the feature function as expected.

Steps to Reproduce

Create a USkeletalMesh and enable the "Enabled with no mask" feature on it. Observe that it has no effect.