Search results sections are not displayed properly when searching British (en_GB) translations

Steps to reproduce

1. Login as Admin
2. Go to Administer Wiki > Content > Localization
3. Set 'Multilingual' to 'No'
4. Set 'Default Language' to 'English (United Kingdom)'
5. Create a page with something distinctive in the title and content (e.g. 'UK')
6. Search by that distinctive words (e.g. 'UK')
7. Click 'Highlight all matches' button on the search result
8. Observe the search result

Expected results

The sections of the search results are translated and displayed properly, e.g. 'Document content', 'Title', 'Location', 'Document source'.

Actual results

When searching a document in the 'English (United Kingdom) - en_GB' language, the sections are not displayed properly (or translated).

They are displayed as: 'doccontentraw_en','doccontent_en', 'title_en'.

The issue reproduces as well if the wiki is set to Multilingual and doesn't reproduce when searching other translations (French of Deutsch).