Fix ghost user warning somewhere else

public/ns/zone.php

@@ -46,11 +46,13 @@ 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
-		$zones = nsListUserZones($_SESSION['username']);
+		if (isset($_SESSION['username'])) {
+			$zones = nsListUserZones($_SESSION['username']);
 
-		if (!empty($zones)) {
-			foreach ($zones as $zone)
-				echo "<option value='" . $zone . "'>" . $zone . "</option>";
+			if (!empty($zones)) {
+				foreach ($zones as $zone)
+					echo "<option value='" . $zone . "'>" . $zone . "</option>";
+			}
 		}
 ?>
 	</select>