[5.2] Smart Search: Fix URL with highlight query

[Hackwar]

Summary of Changes

When the route of an entry in Smart Search isn't a query string, the highlight feature actually can produce invalid URLs. This PR enforces these URLs to be correct.

Testing Instructions

Look at #43397, apply that patch and get the testing plugin. Index an RTF file and search in the frontend for this entry in the search. Click on the URL.

Actual result BEFORE applying this Pull Request

The URL looks something like /tolstoy.rtf&highlight=bunchofbase64gibberish and throws a 404 when clicked.

Expected result AFTER applying this Pull Request

The URL looks something like /tolstoy.rtf?highlight=bunchofbase64gibberish and does not throw a 404 when clicked.

Link to documentations

Please select:

• [ ] Documentation link for docs.joomla.org:

• [X] No documentation changes for docs.joomla.org needed

• [ ] Pull Request link for manual.joomla.org:

• [X] No documentation changes for manual.joomla.org needed

[webnet-assmann]

I have tested this item :white_check_mark: successfully on a5bd855753404f6a164c0475d70b2e263cdaf2b7

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43398.}