[horde] ActiveSync PHP Error

[Philipp Faeustlin]

I get dozens of the following error in my horde.log file

WARN: HORDE PHP ERROR: Argument 1 passed to 
Horde_ActiveSync_Request_Sync::_handleError() must be of the type array, 
null given, called in /usr/share/pear/Horde/ActiveSync/Request/Sync.php 
on line 947 and defined [pid 11437 on line 1353 of 
"/usr/share/pear/Horde/ActiveSync/Request/Sync.php"]

Does someone know why this error occurs?

I think its probably some faulty ActiveSync Device, but I don't know how 
to find out which.

Is there some way to link the apache process id two some ActiveSync device?

Regards

Philipp Fäustlin