Joomla version : 1.5.113
JoomlaComment version : 4.0 RC1
PHP version : 5.2.11
MySQL version : 5.1.36

At the top of every article published I can observe the following expression:
"Notice: Undefined variable: com in xxx \ www \ components \ com_comment \ joscomment \ comment.class.php on line 728 "

Obviously if I turn off "display errors" in the setting of php, the error disappears.

How can I fix this?

Thanks for your work