Handling of gltf meshes with children is still wrong

[0b5vr]

Turned out that what I did in #588 was totally wrong! 🙇

Actual tree of objects are like this:

- `THREE.Group` The target node (that used to be traversed)
    - `THREE.Group` **A group that contains all the mesh primitives** 
        - `THREE.Mesh` A primitive of the target node
        - `THREE.Mesh` A primitive of the target node (2)
    - `THREE.Group` A child node with a mesh
        - `THREE.Group` **A group that contains all the mesh primitives** 
            - `THREE.Mesh` A primitive of the child node, that should not be processed using traverse
            - `THREE.Mesh` A primitive of the child node, that should not be processed using traverse (2)

Seems we have to fix the function gltfExtractPrimitivesFromNode again.