add missing default value

examples/jsm/renderers/nodes/inputs/ColorNode.js

@@ -1,8 +1,9 @@
 import InputNode from '../core/InputNode.js';
+import { Color } from '../../../../../build/three.module.js';
 
 class ColorNode extends InputNode {
 
-	constructor( value ) {
+	constructor( value = new Color() ) {
 
 		super( 'color' );
 

examples/jsm/renderers/nodes/inputs/Vector2Node.js

@@ -1,8 +1,9 @@
 import InputNode from '../core/InputNode.js';
+import { Vector2 } from '../../../../../build/three.module.js';
 
 class Vector2Node extends InputNode {
 
-	constructor( value ) {
+	constructor( value = new Vector2() ) {
 
 		super( 'vec2' );