From 52549ae747613994a8ced4de9b567bc4cc09443f Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Wed, 12 Aug 2020 10:25:49 +0000
Subject: Fix [e87000d8425ab86a]: crash for "fconfigure stdout" in Win32. Even
 though the crash cannot happen in Tcl 8.6, the function
 Tcl_BadChannelOption() was to blame, so better fix that in 8.6 too.

---
 generic/tclIO.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 7abeb68..82eb581 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -7699,7 +7699,7 @@ Tcl_BadChannelOption(
 	}
 	Tcl_ResetResult(interp);
 	errObj = Tcl_ObjPrintf("bad option \"%s\": should be one of ",
-                optionName);
+                optionName ? optionName : "");
 	argc--;
 	for (i = 0; i < argc; i++) {
 	    Tcl_AppendPrintfToObj(errObj, "-%s, ", argv[i]);
-- 
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