Listagem com problema

Pessoal tenho a seguinte mensagem de erro.

Fatal error: Call to a member function getId() on a non-object inC:\xampp\htdocs\cmsbr\VIEW\index.php on line 82

Não consigo entender o porque.

<?php
require_once "../DTO/materiaDTO.php";
require_once '../CTR/materiaCTR.php';
require_once "../CTR/publicidadeCTR.php";

$materiaDTO = new materiaDTO();
$materiaCTR = new materiaCTR();
$listaMateria[] = new materiaDTO();
$materiaCTR->publicar();

$publicidadeCTR = new publicidadeCTR();
$publicidadeCTR->publicarPublicidade();

$materiaDTO->setOp(4);
$listaMateria = $materiaCTR->pesquisarMateria($materiaDTO);

include 'topo.php';
?>
<section class="estrutura">
 <div id="sliderb_container" class="slidshow">

 <!-- Loading Screen -->
 <div u="loading" style="position: absolute; top: 0px; left: 0px;">
 <div style="filter: alpha(opacity=70); opacity:0.7; position: absolute; display: block;
 background-color: #000; top: 0px; left: 0px;width: 100%;height:100%;"> </div>
 <div style="position: absolute; display: block; background: url(../img/loading.gif) no-repeat center center;
 top: 0px; left: 0px;width: 100%;height:100%;"> </div>
 </div>

 <!-- Slides Container -->
 <div u="slides" style="cursor: move; position: absolute; left: 0px; top: 0px; width: 600px; height: 350px;
 overflow: hidden;">
 <?php
 for ($i = 0; $i <= 4; $i++) {
 echo '<div>
 <a href="noticia.php?v=' . $listaMateria[$i]->getId() . '"> <img u=image src="img_materia/' . $listaMateria[$i]->getImagem() . '" /></a>
 <div u="thumb"><a href="noticia.php?v=' . $listaMateria[$i]->getId() . '">' . $listaMateria[$i]->getTitulo() . '</a></div>
 </div>';
 }
 ?>
 </div>

 <!-- ThumbnailNavigator Skin Begin -->
 <div u="thumbnavigator" class="sliderb-T" style="position: absolute; bottom: 0px; left: 0px; height:45px; width:600px;">
 <div style="filter: alpha(opacity=40); opacity:0.4; position: absolute; display: block;
 background-color: #000000; top: 0px; left: 0px; width: 100%; height: 100%;"> </div>
 <!-- Thumbnail Item Skin Begin -->
 <div u="slides">
 <div u="prototype" style="POSITION: absolute; WIDTH: 600px; HEIGHT: 45px; TOP: 0; LEFT: 0;">
 <thumbnailtemplate style="font-family: verdana; font-weight: normal; POSITION: absolute; WIDTH: 100%; HEIGHT: 100%; TOP: 0; LEFT: 0; color:#fff; line-height: 45px; font-size:20px; padding-left:10px;"></thumbnailtemplate>
 </div>
 </div>
 <!-- Thumbnail Item Skin End -->
 </div>
 <!-- ThumbnailNavigator Skin End -->

 <!-- Bullet Navigator Skin Begin -->
 <!-- jssor slider bullet navigator skin 01 -->
 <!-- bullet navigator container -->
 <div u="navigator" class="jssorb01" style="position: absolute; bottom: 16px; right: 10px;">
 <!-- bullet navigator item prototype -->
 <div u="prototype" style="POSITION: absolute; WIDTH: 12px; HEIGHT: 12px;"></div>
 </div>
 <!-- Bullet Navigator Skin End -->

 <!-- Arrow Navigator Skin Begin -->
 <!-- Arrow Left -->
 <span u="arrowleft" class="jssora05l" style="width: 40px; height: 40px; top: 123px; left: 8px;"> </span>
 <!-- Arrow Right -->
 <span u="arrowright" class="jssora05r" style="width: 40px; height: 40px; top: 123px; right: 8px"> </span>
 <!-- Arrow Navigator Skin End -->
 <!-- Trigger -->
 </div>
 <section class="revista"> <a href="#"><img src="img/revista/Revista.jpg" alt="Revista do mês"></a>
 <artigo class="legendarevista">
 </article>
 </section>
 <section class="noticias">
 <?php
 for ($i = 5; sizeof($listaMateria) >= $i; $i++) {
 if ($listaMateria[$i]->getId() != "") {
 echo '<article class="artigos"> <a href="noticia.php?v=' . $listaMateria[$i]->getId() . '"><img src="img_materia/mini_' . $listaMateria[$i]->getImagem() . '">
 <h1>' . $listaMateria[$i]->getTitulo() . '</h1>
 <p>' . $listaMateria[$i]->getLinha_fina() . '</p>
 </a> </article>';
 }
 }
 ?>

 </section>
 <section class="propaganda1" id="p1">
 <img src="img/publicidade/p1.jpg" width="300" height="300">
 <img src="img/publicidade/p2.jpg" width="300" height="300">
 <img src="img/publicidade/p3.jpg" width="390" height="390">
 </section>
 <section class="estruturapropa">
 <section class="propaganda2" id="p2">
 <img src="img/publicidade/p1.jpg" width="300" height="300">
 <img src="img/publicidade/p2.jpg" width="300" height="300">
 <img src="img/publicidade/p3.jpg" width="390" height="390">
 </section>
 <section class="propaganda3" id="p3">
 <img src="img/publicidade/p1.jpg" width="300" height="300">
 <img src="img/publicidade/p2.jpg" width="300" height="300">
 <img src="img/publicidade/p3.jpg" width="390" height="390">
 </section>
 <section class="propaganda4" id="p4">
 <img src="img/publicidade/p1.jpg">
 <img src="img/publicidade/p2.jpg">
 <img src="img/publicidade/p3.jpg">
 </section>
 </section>
 <section class="face">
 <iframe src="http://www.facebook.com/plugins/likebox.php?href=https%3A%2F%2Fwww.facebook.com%2Fpages%2FRevista-ELITE-Magazine%2F696547390365019&width=390&height=590&colorscheme=light&show_faces=true&header=true&stream=true&show_border=false" scrolling="no" frameborder="0" style="border:none; overflow:hidden; height:590px; width: 100% !important;" allowTransparency="true"></iframe>
 </section>
</section>
<div class="clearfix"></div>
<?php
include 'rodape.php';
?>

Parte que esta dando Erro:

 <?php
 for ($i = 5; sizeof($listaMateria) >= $i; $i++) {
 if ($listaMateria[$i]->getId() != "") {
 echo '<article class="artigos"> <a href="noticia.php?v=' . $listaMateria[$i]->getId() . '"><img src="img_materia/mini_' . $listaMateria[$i]->getImagem() . '">
 <h1>' . $listaMateria[$i]->getTitulo() . '</h1>
 <p>' . $listaMateria[$i]->getLinha_fina() . '</p>
 </a> </article>';
 }
 }
 ?>