AMFLoader: fix materialId reference (#30668)

Co-authored-by: Samuel Rigaud <srigaud@duodisplay.com>

examples/jsm/loaders/AMFLoader.js

@@ -236,7 +236,7 @@ class AMFLoader extends Loader {
 
 		function loadMeshVolume( node ) {
 
-			const volume = { name: '', triangles: [], materialid: null };
+			const volume = { name: '', triangles: [], materialId: null };
 
 			let currVolumeNode = node.firstElementChild;