Fix undefined variable

airtime_mvc/application/views/scripts/billing/invoices.phtml

@@ -1,6 +1,7 @@
 <div class="ui-widget ui-widget-content block-shadow clearfix padded-strong billing-panel">
 <H2>Invoices</H2>
 <?php 
+$topTextClass = "";
 if (array_key_exists("planupdated", $_GET))
 {
     $topText = _("<b>Thank you!</b> Your plan has been updated and you will be invoiced during your next billing cycle.");
@@ -30,4 +31,4 @@ foreach ($this->invoices as $invoice) {?>
     
 <?php };?>
 </table>
-</div>
+</div>