Remove unnecessary extra space in dialogs

The hack below in core/misc/dialog/dialog.ajax.js should hide some inputs, but does not work correctly, the views that ends up generating an unnecessary extra space

Problem/Motivation

// Hidden form buttons need special attention. For browser consistency,
// the button needs to be "visible" in order to have the enter key fire
// the form submit event. So instead of a simple "hide" or
// "display: none", we set its dimensions to zero.
// See http://mattsnider.com/how-forms-submit-when-pressing-enter/
var $originalButton = $(this).css({
  width: 0,
  height: 0,
  padding: 0,
  border: 0
});

Proposed resolution

Add display: block to "hide" properly