Ctrl+Z in Frame Graph brokes playground demo

[Dok11]

1. Open https://playground.babylonjs.com/#JWKDME#205 (it’s from this page Babylon.js docs )

2. Open Edit Frame Graph

   

3. Select and Delete this connection
   

   

4. Press Ctrl+Z

5. Now in the scene:
   TypeError: Cannot read properties of null (reading ‘getScene’)
   at new e (shadowGenerator.ts:902:29)
   at t._createShadowGenerator (shadowGeneratorTask.ts:260:33)
   at t._setupShadowGenerator (shadowGeneratorTask.ts:267:18)
   at t.set (shadowGeneratorTask.ts:28:14)
   at t._buildBlock (baseShadowGeneratorBlock.ts:232:30)
   at e.build (nodeRenderGraphBlock.ts:365:14)
   at e.build (nodeRenderGraphBlock.ts:350:23)
   at e.build (nodeRenderGraphBlock.ts:350:23)
   at e.build (nodeRenderGraphBlock.ts:350:23)
   at e.build (nodeRenderGraphBlock.ts:350:23)

6. And after resize window with playground demo:
   Uncaught (in promise) TypeError: Cannot read properties of null (reading ‘getScene’)

Context:

WEBGL2
8.53.0 (Latest)

I did not look deep, but this part looks strange:

The this._light after Ctrl+Z in this case is null but there is only undefined check.

[Evgeni_Popov]

Thanks for reporting, this PR will fix the problem:

FrameGraph: Fix undo/redo in NRGE (#17999)