Fix for consistent WARNING/NOTICES for undefined constants

Fix for consistent WARNING/NOTICES for undefined constants -  See below

var/www/mydomain.com/vendor/dino/dompdf-module/src/DOMPDFModule/Service/DOMPDFFactory.php on line 107
[Mon Jun 24 09:19:42 2013] [error] [client 35.8.133.99] FastCGI: server "/var/www/fastcgi/php5.fastcgi" stderr: PHP message: PHP Notice:  Use of undefined constant DOMPDF_ADMIN_PASSWORD - assumed 'DOMPDF_ADMIN_PASSWORD' in /var/www/mydomain.com/vendor/dino/dompdf-module/src/DOMPDFModule/Service/DOMPDFFactory.php on line 107
[Mon Jun 24 11:20:53 2013] [error] [client 35.8.133.99] FastCGI: server "/var/www/fastcgi/php5.fastcgi" stderr: PHP message: PHP Notice:  Use of undefined constant DOMPDF_ADMIN_USERNAME - assumed 'DOMPDF_ADMIN_USERNAME' in /var/www/mydomain.com/vendor/dino/dompdf-module/src/DOMPDFModule/Service/DOMPDFFactory.php on line 107
[Mon Jun 24 11:20:53 2013] [error] [client 35.8.133.99] FastCGI: server "/var/www/fastcgi/php5.fastcgi" stderr: PHP message: PHP Notice:  Use of undefined constant DOMPDF_ADMIN_PASSWORD - assumed 'DOMPDF_ADMIN_PASSWORD' in /var/www/mydomain.com/vendor/dino/dompdf-module/src/DOMPDFModule/Service/DOMPDFFactory.php on line 107