var current_score_str:String = shield_txt.text as String;
				var current_score_int:Number = current_score_str as Number;
				current_score_int += 1;
				current_score_str = current_score_int as String;
				shield_txt.text = current_score_str;


error:

TypeError: Error #2007: Parameter text must be non-null.
	at flash.text::TextField/set text()
	at Fight/::next_slap()
	at flash.utils::Timer/flash.utils:Timer::_timerDispatch()
	at flash.utils::Timer/flash.utils:Timer::tick()