Fix isCube property not set when no texture is loaded yet

src/Materials/Textures/baseTexture.ts

@@ -173,13 +173,14 @@ export class BaseTexture implements IAnimatable {
     @serialize()
     public anisotropicFilteringLevel = BaseTexture.DEFAULT_ANISOTROPIC_FILTERING_LEVEL;
 
+    private _isCube = false;
     /**
      * Define if the texture is a cube texture or if false a 2d texture.
      */
     @serialize()
     public get isCube(): boolean {
         if (!this._texture) {
-            return false;
+            return this._isCube;
         }
 
         return this._texture.isCube;
@@ -187,10 +188,10 @@ export class BaseTexture implements IAnimatable {
 
     public set isCube(value: boolean) {
         if (!this._texture) {
-            return;
+            this._isCube = value;
+        } else {
+            this._texture.isCube = value;
         }
-
-        this._texture.isCube = value;
     }
 
     /**

src/Materials/Textures/cubeTexture.ts

@@ -305,7 +305,7 @@ export class CubeTexture extends BaseTexture {
         if (!this._texture) {
             const scene = this.getScene();
             if (this._prefiltered) {
-                this._texture = this._getEngine()!.createPrefilteredCubeTexture(this.url, scene, 0.8, 0, this._delayedOnLoad, undefined, this._format, undefined, this._createPolynomials);
+                this._texture = this._getEngine()!.createPrefilteredCubeTexture(this.url, scene, 0.8, 0, this._delayedOnLoad, undefined, this._format, forcedExtension, this._createPolynomials);
             }
             else {
                 this._texture = this._getEngine()!.createCubeTexture(this.url, scene, this._files, this._noMipmap, this._delayedOnLoad, null, this._format, forcedExtension, false, 0, 0, null, this._loaderOptions);