GLTFLoader: Make `navigator` access more robust. (#24989)
GLTFLoader: Make `navigator` access more robust. (#24989)

* GLTFLoader: headless

This pull request will only request navigator if it is defined, as GLTFLoader attempts to retrieve navigator, but this will throw an error for headless gltf support.

* Update GLTFLoader.js

Co-authored-by: Michael Herzog <f6aeef0c0610dd1547ce61332ac92e282a679af1@human-interactive.org>
mrdoob/three.js,mrdoob/three.js