When the summary field is empty use another field for search results

Problem/Motivation

The summary field is used to display search results for site search. When the Summary field has no value search results do not display a page summary. We need a solution so that when the Summary field has no value search defaults elsewhere for the search snippet.

Acceptance criteria

Given I'm an anonymous user
When I perform a search
And the resulting page/s have no value in the Summary field
Then I still see a search result snippet