Hello,
After I updated to Babylonjs 4.0, I noticed that each line of code I wrote using:
new BABYLON.TransformNode('name')
throws an error like that:
Uncaught (in promise) TypeError: Cannot read property 'getUniqueId' of null
    at t.e (babylon.js:16)
    at new t (babylon.js:16)
    at new IslandsToPathConverter (IslandsToPathsConverter.ts:53)
    at GameLoop.<anonymous> (GameLoop.ts:249)
    at step (GameLoop.ts:45)
    at Object.next (GameLoop.ts:26)
    at fulfilled (GameLoop.ts:17)
This is corrected by adding the scene as an argument:
new BABYLON.TransformNode('name', scene)
Is that normal?