Don't add crm-codes as pa-codes

public/typo3conf/ext/ep_theme/Classes/DataProcessing/ContextProcessor.php

@@ -118,11 +118,11 @@ class ContextProcessor implements DataProcessorInterface
      */
     private function getCookieData()
     {
-        if ($_COOKIE['ep_trk']) {
+        if (isset($_COOKIE['ep_trk']) && preg_match('/^PA\d{4}$/', $_COOKIE['ep_trk'])) {
             return $_COOKIE['ep_trk'];
         }
 
-        return '';
+        return null;
     }
 
     /**