add missing terminator argument for ast_event_subscribe().

Without it the function will randomly walk on the stack
possibly causing a panic


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@131206 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_agent.c

@@ -2464,7 +2464,7 @@ static int load_module(void)
 	/* Dialplan Functions */
 	ast_custom_function_register(&agent_function);
 
-	agent_devicestate_sub = ast_event_subscribe(AST_EVENT_DEVICE_STATE, agent_devicestate_cb, NULL);
+	agent_devicestate_sub = ast_event_subscribe(AST_EVENT_DEVICE_STATE, agent_devicestate_cb, NULL, AST_EVENT_IE_END);
 
 	return AST_MODULE_LOAD_SUCCESS;
 }