anchor.diff:  
   						var tangent = geometry.attributes[ "tangent" ];
   
  -						if ( attributes["tangent"] >= 0 && tangent ) {
  +						if ( attributes["tangent"] >= 0 && tangent != null ) {
   
   							var tangentSize = tangent.itemSize;
   
  
positive.code: 
  						var color = geometry.attributes[ "color" ];
  
  						if ( attributes["color"] >= 0 && color ) {
  
  							var colorSize = color.itemSize;
  
  
negative.code: 
  						var normal = geometry.attributes[ "normal" ];
  
  						if ( attributes["normal"] >= 0 && normal != null) {
  
  							var normalSize = normal.itemSize;
  
  