coverity#708651 Uninitialized pointer field

Change-Id: If2c5d406994902839c4c81a947fc46a06056fe90
given the explanation of MenuFloatingWindow::InitClipRegion()...

should not be virtual then prior to 95711f5b9e7b6a982d1762d37d5a38e0f40b86f9
the menu ImplInitClipRegion had nothing to do with the outdev
ImplInitClipRegion and so all the original ImplInitClipRegion calls here should
now be routed to InitMenuClipRegion which was removed by "In fact
InitMenuClipRegion() is unused" so restore that

Change-Id: Id208b30561803ee774e10d44e19ed0808f824766