From 56402e84b5ba242214ff4d3c4a647413cbe60ff3 Mon Sep 17 00:00:00 2001
From: Vladislav Vaintroub <wlad@mariadb.com>
Date: Mon, 16 Mar 2020 11:43:30 +0100
Subject: [PATCH] MDEV-21824 
Crash in convert_error_message

restore check for client charset_info == NULL, which was previously
removed in MDEV-8844
---
 sql/sql_error.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sql/sql_error.cc b/sql/sql_error.cc
index 4045f30a6bd..e5dda9904d2 100644
--- a/sql/sql_error.cc
+++ b/sql/sql_error.cc
@@ -947,7 +947,7 @@ size_t convert_error_message(char *to, size_t to_length, CHARSET_INFO *to_cs,
   /* Make room for the null terminator. */
   to_length--;
 
-  if (to_cs == &my_charset_bin)
+  if (!to_cs || to_cs == &my_charset_bin)
     to_cs= system_charset_info;
   uint32 cnv_length= my_convert_using_func(to, to_length,
                                            to_cs,