Problems with glow layer once parsed from a serialized scene

[julien-moreau]

Bug

• Bug repro on playground:
• Expected result: the glow layer is parsed and no error happen while loading the scene
• Current result: the scene looks loaded correctly but an error happens in the console only if a glow layer is added to the source scene being serialized.

[julien-moreau]

With this new playground, you can also see that the glow layer is parsed because it is working in the scene: https://www.babylonjs-playground.com/#558RAP#8 but the error still happens in the console.