How do I correct this notice: undefined variable?

  1  <?php
  2  	    session_start();
  3  	    if (!isset($_SESSION['username'])) {
  4  	    }
  5  	    else{
  6  		$uname=$_SESSION['username'];
  7  	    }
  8  	    
  9  	    if($uname!=""){
 10  		echo "<a class='brand' href='home.php'>Bais City Division LRMS</a>";?>
 11  		<div class="nav-collapse">
 12  		<ul class="nav">
 13  		    <li><a href="home.php">Home</a></li>
 14  		    <li><a href="about.php">About</a></li>
 15  		    <li class="active"><a href="contact.php">Contact</a></li>              
 16  		</ul>
 17  		<a class="btn btn-primary pull-right" href="logout.php" title="Click to logout"><?=$_SESSION['username']?></a>
 18  	    <?php
 19  	    }
 20  	    else{
 21  		echo "<a class='brand' href='index.php'>Bais City Division LRMS</a>";?>
 22  		<div class="nav-collapse">
 23  		<ul class="nav">
 24  		    <li><a href="index.php">Home</a></li>
 25  		    <li><a href="about.php">About</a></li>
 26  		    <li class="active"><a href="contact.php">Contact</a></li>              
 27  		</ul>
 28  	     <?php
 29  	    }
 30  		if($uname!=""){
 31  		}
 32  		else{
 33  	    ?>
 34  	    <a class="btn btn-primary pull-right" href="filter.php" title="Click to login"></button></a>";
 35  	    }
 36  	    else{
 37  	?>
 38             <a href="index.php?categ=Images"><button class="btn btn-inverse">^__i class=" icon-picture icon-white"__^</i__^Images</button></a>
 39  	   <a href="index.php?categ=Music"><button class="btn btn-success">^__i class=" icon-music icon-white"__^Music</button></a>
 40             <a href="index.php?categ=Videos"><button class="btn btn-primary" id="clickme">^__i class="icon-film icon-white">Videos</button></a>
 41             <a href="index.php?categ=Documents"><button class="btn btn-info">^__i class="icon-file icon-white">Documents</button></a>
 42             <a href="index.php?categ=Text Files"><button class="btn btn-warning">^__i class="icon-file icon-white">Text Files</button></a>
 43             <a href="index.php?categ="><button class="btn">^__i class="icon-check">All Files</button></a>
 44  	<?php } ?>