except.cxx: Fix pTypeDescr is unknown in this context error

Change-Id: Ic47f69b01cf17a55901e9e3541419d9f477d9585
Reviewed-on: https://gerrit.libreoffice.org/13210
Tested-by: David Ostrovsky <david@ostrovsky.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>