Fix to MXS-212: https://mariadb.atlassian.net/browse/MXS-212

The listener DCB is now properly closed instead of just being removed from the poll set.

server/modules/protocol/mysql_client.c

@@ -1771,7 +1771,7 @@ gw_client_close(DCB *dcb)
             dcb->state == DCB_STATE_NOPOLLING ||
             dcb->state == DCB_STATE_ZOMBIE)
         {
-		if (!DCB_IS_CLONE(dcb)) CHK_PROTOCOL(protocol);
+		if (!DCB_IS_CLONE(dcb) && protocol) CHK_PROTOCOL(protocol);
         }
 #endif
 	LOGIF(LD, (skygw_log_write(LOGFILE_DEBUG,

server/modules/protocol/mysql_common.c

@@ -128,7 +128,10 @@ void mysql_protocol_done (
         MySQLProtocol* p;
         server_command_t* scmd;
         server_command_t* scmd2;
-        
+
+	if(dcb->protocol == NULL)
+	    return;
+
         p = (MySQLProtocol *)dcb->protocol;
         
         spinlock_acquire(&p->protocol_lock);