Nulling instead of deleting in dispose().

Still waiting for an "official" recommendation from a VM guy though.

src/core/Geometry.js

@@ -742,7 +742,7 @@ THREE.Geometry.prototype = {
 
 		for ( var property in this ) {
 
-			delete this[ property ];
+			this[ property ] = null;
 
 		}
 

src/core/Object3D.js

@@ -355,7 +355,7 @@ THREE.Object3D.prototype = {
 
 		for ( var property in this ) {
 
-			delete this[ property ];
+			this[ property ] = null;
 
 		}
 

src/materials/Material.js

@@ -122,7 +122,7 @@ THREE.Material.prototype.dispose = function () {
 
 	for ( var property in this ) {
 
-		delete this[ property ];
+		this[ property ] = null;
 
 	}
 

src/textures/Texture.js

@@ -83,7 +83,7 @@ THREE.Texture.prototype = {
 
 		for ( var property in this ) {
 
-			delete this[ property ];
+			this[ property ] = null;
 
 		}