Fix the save button disappearing on certain pages in Firefox

If the first thing on the page is an image, then we'll try to select
it in Firefox, and get a JS error because .data( 'view' ) is undefined.

It turned out that MWBlockImageNode's onSetup() didn't call the parent
implementation, and all the way up in ve.ce.View.onSetup is where
we set .data( 'view' )

Bug: 51986
Change-Id: I0de3692566b0aa02a229054e07767e45fd5d4a49