Fix ghost user warning somewhere else

public/ns/zone.php

@@ -46,12 +46,14 @@ if (isset($_POST['domain']) AND isset($_SESSION['username'])) {
 	<label for="zone">Zone</label>
 	<select required="" name="zone" id="zone">
 		<option value="" disabled="" selected="">-</option><?php
+		if (isset($_SESSION['username'])) {
 			$zones = nsListUserZones($_SESSION['username']);
 
 			if (!empty($zones)) {
 				foreach ($zones as $zone)
 					echo "<option value='" . $zone . "'>" . $zone . "</option>";
 			}
+		}
 ?>
 	</select>
 	<br>