The documentation for `freeze()` says that:
- If `script` is `None`, all files in `path` will be frozen.
- If `script` is an iterable then `freeze()` is called on all items of the
iterable.
This commit makes sure this behaviour is followed when an empty tuple/list
is passed in for `script` (previously an empty tuple/list froze all files).
Fixes issue #14125.
Signed-off-by: Damien George <damien@micropython.org>
51d05c442a