set read codec to NULL for reset is better

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@10011 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_conference/mod_conference.c

@@ -4548,7 +4548,7 @@ SWITCH_STANDARD_APP(conference_function)
 	conference_del_member(member.conference, &member);
 
 	/* Put the original codec back */
-	switch_core_session_set_read_codec(member.session, read_codec);
+	switch_core_session_set_read_codec(member.session, NULL);
 
 	/* Clean Up.  codec_done(X): is for error situations after the codecs were setup and done: is for situations before */
   codec_done1: