Geometry: Avoid creating undefined uvs in .fromBufferGeometry(). Fixes #5567.

src/core/Geometry.js

@@ -140,8 +140,13 @@ THREE.Geometry.prototype = {
 			var vertexColors = colors !== undefined ? [ scope.colors[ a ].clone(), scope.colors[ b ].clone(), scope.colors[ c ].clone() ] : [];
 
 			scope.faces.push( new THREE.Face3( a, b, c, vertexNormals, vertexColors ) );
+
+			if ( uvs !== undefined ) {
+
 				scope.faceVertexUvs[ 0 ].push( [ tempUVs[ a ], tempUVs[ b ], tempUVs[ c ] ] );
 
+			}
+
 		};
 
 		if ( indices !== undefined ) {