Spline Mesh With Negative Start and End Scale Has Broken Lightmap

When you have a negative start and end Scale for a spline mesh the resulting lightmap that gets baked for the mesh will be incorrect.

1. Open attached project
2. Open the BP asset named "spline"
3. Change the Start and End Scale (x,y) to (-1,-1)
4. Bake Lighting

RESULT
The baked lighting is incorrect on the mesh.

EXPECTED
The baked lighting has correct shadowing for negative scale.