Blender Git Loki

Another attempt to fix the failure of SVertex::getFEdge due to a discontinuity
of underlying FEdges introduced by chaining operations. The material of a
smooth FEdge is identified by the material index of the FEdge and the array
of materials in the SShape to which the first SVertex (i.e., vertexA) of the
FEdge belong. The present fix makes sure that the material index refers to the
intended array of materials, to avoid inconsistent reference and out-of-index
errors that lead to a crash.