REST script error

I get the following error with the code below: Error: Unable to get property 'Title' of undefined or null reference

function getListItems(url, listname, complete, failure) {

    // Executing our items via an ajax request
    $.ajax({
        url: url + "/_api/web/lists/getbytitle('" + listname + "')/items",
        method: "GET",
        headers: { "Accept": "application/json; odata=verbose" },
        success: function (data) {
            complete(data); // Returns JSON collection of the results
        },
        error: function (data) {
            failure(data);
        }
    });
	
 function complete(data) {
    var truckPie = new truck2pie();
	
	for (i=0;i<=data.d.results.length; i++)
	 {  	 
	  console.log(data.d.results[i].Title);
	  truckPie.addTruck([b]data.d.results[i].Title[/b],  data.d.results[i].NumberOfTrucks);  //<---
	 }
 }
 

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