[LyX/master] Fix display of comment char in "lyxlex" debug channel

[Jean-Marc Lasgouttes]

commit 430c41cd05310e1609e59443927234fcb4493f1b
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Sun Jul 16 20:15:48 2023 +0200

    Fix display of comment char in "lyxlex" debug channel
---
 src/Lexer.cpp |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/Lexer.cpp b/src/Lexer.cpp
index ab052f5..eabe694 100644
--- a/src/Lexer.cpp
+++ b/src/Lexer.cpp
@@ -300,7 +300,7 @@ bool Lexer::Pimpl::next(bool esc /* = false */)
 			string dummy;
 			getline(is, dummy);
 
-			LYXERR(Debug::LYXLEX, "Comment read: `" << c << dummy << '\'');
+			LYXERR(Debug::LYXLEX, "Comment read: `" << string(1, c) << dummy << '\'');
 #else
 			// unfortunately ignore is buggy (Lgb)
 			is.ignore(100, '\n');