Prevent Uncaught Exception in NullEngine.dispose

[barroij]

I am having an uncaught exception when using BaylonJs in a NodeJs environment because of a call to window.removeEventListener from NullEngine.dispose().

This PR adds extra checks to make that addEventListener/removeEventListener do exist and are functions before calling them.

This PR comes along with #13401 in order to improve BabylonJs usability in non-browser environment

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[barroij]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s). To prevent this PR from going to the changelog marked it with the "skip changelog" label.

Hmmmn, I cannot edit labels, but anyway I'm not sure that such a minor change is worth being mentioned in the ChangeLog.

[bjsplat]

Snapshot stored with reference name:
refs/pull/13406/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13406/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13406/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/13406/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/13406/merge
https://gui.babylonjs.com/?snapshot=refs/pull/13406/merge
https://nme.babylonjs.com/?snapshot=refs/pull/13406/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/13406/merge#BCU1XR#0

[bjsplat]

Visualization tests for webgl1 have failed. If some tests failed because the snapshots do not match, the report can be found at

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13406/merge/testResults/webgl1/index.html

If tests were successful afterwards, this report might not be available anymore.

[sebavan]

LGTM, but let s wait on @RaananW feedback. Could you fix the formatting and linting ? I guess it is the only missing part to merge it

[sebavan]

@barroij would be great if you can fix lint and format ?

[RaananW]

LGTM! just formatting

[barroij]

@RaananW formatting done!