APEX Plugin - Destructible Mesh creation no longer creates/assigns Mesh Material

Destructible mesh material creation no longer creates/assigns DM array element with material from mesh.

Workaround: Assign material manually after creating Destructible mesh

Confirmed in MAIN @ CL 4668817

1. Enable APEX Destruction plugin
2. Import or create a static mesh with a material
3. Right-Click on mesh in content browser -> 'Create Destructible Mesh'

4.20 Result: The Destructible mesh has 2 array elements in Skeletal Mesh -> Materials, with mat 0 being the material on the mesh. (With the other element being WorldGridMaterial)

4.21 Result: The Destructible mesh has 1 array element. (WorldGridMaterial)