Remove redundant (void*)-1 pointer fixups
Remove redundant (void*)-1 pointer fixups

We never set internal pointers in children/nodes array to -1 so we don't
need to handle this - fixup code only runs for a successful parse so we
can assume that everything is correct.

jkuhlmann/cgltf,jkuhlmann/cgltf,jkuhlmann/cgltf