Related: rhbz#1076264 intermittent a11y crash in calc

http://retrace.fedoraproject.org/faf/reports/338291/

this crash refuses to be captured alive. But seeing as
we sometimes check mpViewShell against NULL and sometimes check
GetViewData against NULL its worth making those checks everytime
for consistency

see also...

rhbz#923993 rhbz#896711 rhbz#602273 rhbz#577595 lp#811057 lp#760665

Change-Id: I5553848018f500b63ade60bcfc756a736b27c64f