OTRS error message on obtaining workorder information

[artur4]

When user clicks on "WorkOrder Information" link within Change, the following error message is shown up:

Software error:
Can't use an undefined value as a SCALAR reference at /opt/otrs//Kernel/System/ITSMChange/ITSMWorkOrder.pm line 2491.

It looks, like attachment to this workorder got corrupted.
Any idea, how the issue ban be fixed? Is there any way to delete this attachment.

We use OTRS 3.0.8 version with ITSM 3.0.4

Thank you
Artur