Merge pull request #10294 from lasdghawiv/MultiMaterial_isArray_check

MultiMaterial.js cross-frame array support

src/materials/MultiMaterial.js

@@ -10,7 +10,7 @@ function MultiMaterial( materials ) {
 
 	this.type = 'MultiMaterial';
 
-	this.materials = materials instanceof Array ? materials : [];
+	this.materials = Array.isArray(materials) ? materials : [];
 
 	this.visible = true;