[Sugar Version 5.2.0l (Build 5843)] undefined variable btracker in EmailMan.php

[sugarstefano]

My MS-DOS console shows the following message
PHP Notice : undefined variable btracker in EmailMan.php
running the job Mass Email Campaign

As follow my system details
S.O. : Win2003SBS
Apache : 2.0.63
PHP : 5.2.8
MySQL : 5.0.83community
SugarCE : Version 5.2.0l (Build 5843)

Before upgrading to this Sugar Version i was running a Version 4.5.1g (Build 1003) and i never got that PHP notice

Any suggestion would be apprecciated.
Thanks in advance for your help.
Kind regards,
Stefano Campri