TypeError: event.target is undefined

[aHMAD_SQaLli]

hello

if there is just the first function it run very good but if I add the second I get the message in Firefox " TypeError: event.target is undefined "

(function(){
	
	document.getElementById("ta").onclick = function(){ ta(); };	
	function ta(){
			
			var tav = document.getElementById("ta").value, ta = document.getElementById("ta");
			ta.setAttribute('style','height:200px;')
	}
})();
window.onclick = function(event) {
	
	var tav = document.getElementById("ta").value, ta = document.getElementById("ta");
	if (! event.target.matches('#ta')) {
		
		if( tav == "" ){
			
			ta.setAttribute('style','height:25px;');
		}
		else if( tav !== "" ){
			
			ta.setAttribute('style','height:200px;');
		}
	}
}
(function(){
	
	document.getElementById("close").onclick = function(){hide_notify();};	
	function hide_notify(){
		
		var notify = document.getElementById("notify");
		notify.parentElement.removeChild(notify);
	}
})();

I'm still new in JavaScript so I have no idea what is going on !

thanks.

[aHMAD_SQaLli]

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