AXAPTA terminate AOS

This code doesn't give compile error. Actually code has mistake. It occurs error 174 and terminates AOS:

    select firstonly * from ord join rel join obj
        where ord.ServiceOrderId == rel.RelKeyId &&
            rel.RelTableId == ord.TableId &&
            obj.ServiceObjectId == rel.ServiceObjectId &&
            ( L_ItemSerialNum.valueStr()== obj.ItemSerialNum || (!L_ItemSerialNum)) &&
            ( L_SMAServiceObjectId.valueStr()== rel.ServiceObjectId || (!L_SMAServiceObjectId));

After this fix there is no terminate anymore:
    select firstonly * from ord join rel join obj
        where ord.ServiceOrderId == rel.RelKeyId &&
            rel.RelTableId == ord.TableId &&
            obj.ServiceObjectId == rel.ServiceObjectId &&
            ( L_ItemSerialNum.valueStr()== obj.ItemSerialNum || (!L_ItemSerialNum.valueStr())) &&
            ( L_SMAServiceObjectId.valueStr()== rel.ServiceObjectId || (!L_SMAServiceObjectId.valueStr()));

I made a bit search at internet and learned error 174 occurs even with perfect code parts...