I'm trying to create a dynamic list of inputs from a text file but I'm having trouble ignoring undefined elements. Here's the code:

Code Actionscript:
myData = new LoadVars() 
        myData.ref = this 
        myData.onLoad = function(succes){ 
                for(var i=0; i<20; i++){
					this.ref["id_"+i].html = true;
					if (this.ref["id_"+i] != 0 )
                    this.ref["id_"+i].htmlText = "<b>"+this["id_"+i]+"</b>" 					
					else if (this.ref["id_"+i] == undefined)
						this.ref["id_"+i].htmlText = "<b>"+0+"</b>"						
            } else trace("Error loading data");			

and the txt file is as below:

The problem is that as the txt file doesn't have an element with "id_3", its value is set to be "undefined". How to change it so that if the txt file does not contain an id, it's value is set to be "0"?