Use a default parameter for renderCallDepth

src/renderers/WebGLRenderer.js

@@ -874,7 +874,7 @@ function WebGLRenderer( parameters ) {
 
 	this.compile = function ( scene, camera ) {
 
-		currentRenderState = renderStates.get( scene, 0 );
+		currentRenderState = renderStates.get( scene );
 		currentRenderState.init();
 
 		scene.traverseVisible( function ( object ) {

src/renderers/webgl/WebGLRenderStates.d.ts

@@ -22,7 +22,7 @@ interface WebGLRenderState {
 export class WebGLRenderStates {
 
 	// renderCallDepth indexes start from 0.
-	get( scene: Scene, renderCallDepth: number ): WebGLRenderState;
+	get( scene: Scene, renderCallDepth?: number ): WebGLRenderState;
 	dispose(): void;
 
 }

src/renderers/webgl/WebGLRenderStates.js

@@ -61,7 +61,7 @@ function WebGLRenderStates() {
 
 	let renderStates = new WeakMap();
 
-	function get( scene, renderCallDepth ) {
+	function get( scene, renderCallDepth = 0 ) {
 
 		let renderState;