Resolves: #i124095# Multiple IAccessible and IAccessible2...

interface methods do not check for NULL pointer access, nor do they trap
exceptions

Fixed by Michael Curran
(cherry picked from commit 113171f2a5d726af6c5266e98e8e790ac6729d2d)

Conflicts:
	winaccessibility/source/UAccCOM/MAccessible.cxx

Change-Id: I28d4b885a6c2db487c2754c2ca11290b3844570b
Reviewed-on: https://gerrit.libreoffice.org/7689
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>