The call to 'AccObjectManagerAgent::GetIAccessibleFromResID'
may set 'pImAcc' to nullptr here (s.
'AccObjectWinManager::GetIAccessibleFromResID', which is called
from there), so handle that case gracefully.
Change-Id: I0dbd48974fd012ff086835b147cd9b9cfc8a052b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/95430
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
