Switch step on an abstract IDOC in a BPM

Hi Experts,

I have IDOC mapping wich filters the items.

is some case all the items are filtered, unfortunatly the idoc item segment is mandatory. I'm trying to create a BPM to Cancel the message if not items is left.

the easiest way I found is to duplicate the item in the mapping and to map default value to the second item.

I'm trying to use a BPM to detect that only the dummy item is available and to cancel it.

in the BPM I'm using a switch to test the result of my mapping, to check the value of an item field.but this does not seem to work.

the mapping seems ok.

I ckecked the Workflow and the container the switch step is testing is empty.

&HRMD_ABA04_OUT.PAYLOAD.OBJID& != 'DO_NOT_SEND'{TYPE=SWFXST_STRING}

this field is an item field.

any idea why it's empty ?

thanks,

abdellatif