Allow the existence of a VME metaobject to be asserted

Allow the existence of a VME metaobject to be asserted

Test for the existence of a VME metaobject.  Otherwise, assertion of
a static cast result is not meaningful.

Change-Id: Ic9e9c38e5dce65c41d20e405c33e179334c37b00
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>
Reviewed-by: Chris Adams <christopher.adams@nokia.com>