Bug #3296 SET character_set_results=NULL crashes server

Description:
On Mac OS X, I can set character_set_results to NULL
and retrieve the value:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@character_set_results;
+-------------------------+
| @@character_set_results |
+-------------------------+
| NULL                    |
+-------------------------+
1 row in set (0.00 sec)

But on Red Hat or Gentoo Linux, the server crashes:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@character_set_results;
ERROR 2013 (HY000): Lost connection to MySQL server during query

How to repeat:
See above.

Additional information: The crash is specific to the use of SELECT @@var_name
form.  Retrieving the value using SHOW VARIABLES works fine:

mysql> set character_set_results=null;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'character\_set\_results';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| character_set_results | NULL  |
+-----------------------+-------+
1 row in set (0.00 sec)

Paul I tested on Windows and Suse 9.0 with a server built with 1 day older BK
4.1 tree without to crash.

Sorry Paul,

But works for me fine too.

Sinisa,

What kind of system did you try it on? I already indicated below
that it happens only on some systems.

I'm disappointed you declare it not a bug, given that it's a trivial
way to crash the server.  If you tell me what information would be
helpful, I'll try to provide it.

This was tested on both Linux and Windows.

ChangeSet 
  1.1746 04/03/30 23:38:56 bell@sanja.is.com.ua +3 -0 
  null processing for character_set_results (BUG#3296)

Thank you for bugreport. Patch for this bug is pushed to our internal source 
repository and will be present in next release of server 4.1