when we try to call PyUNO_callable object that doesn't have __class__ attribute

Change-Id: Ia05f70d70f248d50aa141b09625f7ec50189e1dd
Reviewed-on: https://gerrit.libreoffice.org/4309Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>