[PATCH v2] Fix make-custom-port in case encoding is #f

Hi Maxime,
Thanks for hint with the explanation. I'm still learning. 
Below the second try.

Best Regards
Hannes


From 5eb06c5d22799170289ab55ab5a8eab45a98b390 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hannes=20M=C3=BCller?= <>
Date: Sun, 2 Feb 2025 21:32:18 +0100
Subject: [PATCH v2] Fix make-custom-port in case encoding is #f

* module/ice-9/custom-ports.scm (make-custom-port): Code fails if
(fluid-ref %default-port-encoding) returns #f. In fact this was the
case why readline support on MSYS2 failed for guile 3.0.10, ref.
https://github.com/msys2/MSYS2-packages/issues/5079
But later used canonicalize-encoding is prepared to handle #f for
encoding. So allow encoding to also handle this case.
---
 module/ice-9/custom-ports.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/module/ice-9/custom-ports.scm b/module/ice-9/custom-ports.scm
index 6010fd94f..c4376db7b 100644
--- a/module/ice-9/custom-ports.scm
+++ b/module/ice-9/custom-ports.scm
@@ -127,7 +127,7 @@
           (id "custom-port")
           (print (make-default-print #:id id))
           (truncate default-truncate)
-          (encoding (string->symbol (fluid-ref %default-port-encoding)))
+          (encoding (and=> (fluid-ref %default-port-encoding) string->symbol))
           (conversion-strategy (fluid-ref %default-port-conversion-strategy))
           (close-on-gc? #f))
   "Create a custom port whose behavior is determined by the methods passed
-- 
2.39.5