add internal texture during swap and die if it does not currently exist

src/Materials/Textures/internalTexture.ts

@@ -454,6 +454,11 @@ export class InternalTexture {
         if (index !== -1) {
             cache.splice(index, 1);
         }
+
+        var index = cache.indexOf(target);
+        if (index === -1) {
+            cache.push(target);
+        }
     }
 
     /**

src/Misc/brdfTextureTools.ts

@@ -62,6 +62,7 @@ export class BRDFTextureTools {
 
                 // Cleanup
                 engine.restoreDefaultFramebuffer();
+                engine._releaseTexture(texture);
                 engine._releaseFramebufferObjects(expandedTexture);
                 if (rgbdPostProcess) {
                     rgbdPostProcess.dispose();