[Fixed] issue during empty BT-fields

src/Modules/Application/Model/Order.php

@@ -90,6 +90,11 @@ class Order extends Order_parent
         $aBtIndividualFields = (array)$oConfig->getConfigParam('d3xrechnung_BT_ORDERFIELDS_INDIVIDUAL');
 
         $aFields = unserialize($sFields);
+		
+		if ($aFields === false) {
+			$aFields = array();
+		}
+
         foreach ($aBtIndividualFields as $key => $Field)
         {
             if(!key_exists($Field, $aFields))