Chunked input/output port without any content raises an error by set-port-position!

[Takashi Kato]

This should not raise an error.

(import (binary io))

(define in/out (open-chunked-binary-input/output-port))
(set-port-position! in/out 0)

[Takashi Kato]

Checking chunk size (Fixes #179)

→ <<cset 4cfae62a2fd7>>