Fixed: "cannot read property '_tokenScrollView' of null."

This error could occur when interacting with token fields.
Fixed: orphan token field autocomplete menus.

If the parent or grandparent window of a token field which was showing an autocomplete menu was closed, the menu would stick around even that the token field was gone.

This fix makes the token field autocomplete menu a proper child window which should also ensure it moves as needed if the parent window moves.