ViewsReferenceFieldFormatter does not check for headers set to show on empty.

Problem/Motivation

If you have view with a header, and the header is set to "Display even if view has no result.", the header is not shown when there is no result.

Steps to reproduce

• 1. Create a new view
• 2. Add a Header (global text area will work). and check the box for "Display even if view has no result".
• NOTE: Do not set any other exposed inputs.
• 3. Add the view to a page using a viewreference field
• 4. View the page when there is no results for the view. The view is not shown

Proposed resolution

See patch. We need to check for the existence of a header, then check if that header is set to show when the view is empty.

Remaining tasks

Review and test patch once uploaded