squirrelmail, debian testing [Fatal error: Call to a member function on a non-object...]

[Rafal Jankowski <rafj@doraco.pl>]

php4         4.4.2-1
apache-ssl   1.3.34-2
squirrelmail 1.4.5-2

I use squirrelmail from debian testing and for a few months and get the 
following php error:

Fatal error: Call to a member function on a non-object in 
/usr/share/squirrelmail/src/read_body.php on line 431

when I enter any attachment twice during one session. I have to log out 
and log in again to read attachment again.
Thanks in advance for any suggestions.