MeshFaceMaterial: More robust check.

src/materials/MeshFaceMaterial.js

@@ -6,7 +6,7 @@ THREE.MeshFaceMaterial = function ( materials ) {
 
 	console.error( 'THREE.MeshFaceMaterial has been removed.' );
 
-	var material = materials !== undefined ? materials[ 0 ] : new THREE.MeshBasicMaterial();
+	var material = Array.isArray( materials ) ? materials[ 0 ] : new THREE.MeshBasicMaterial();
 	material.materials = []; // temporal workaround
 
 	return material;