URL pagination issue when highlight is present

[ZeGoose95]

Hello,

I run mybb v1.8.39 with plugin "Google SEO (Updated for PHP 8) (1.8.6)".

A user have reported an issue. After a search, with the "highlight" param in the query, the pagination links are not OK: there are two '?' in the URL.

Obtained link:
https://website/SEO-URL-OF-SUBJECT?page=2?highlight=SEARCHED_KEYWORD

Should be:
https://website/SEO-URL-OF-SUBJECT?page=2&highlight=SEARCHED_KEYWORD

Real example: https://www.japancar.fr/forum/Sujet-ACTU-HONDA?highlight=honda (then, see the pagination links on the page)

Not sure if the issue come from mybb 1.8.39 or the Google SEO plugin, but I assume should be more on plugin side.
I have the same content for my htaccess file than the one in the repo.

[ZeGoose95]

I propose a fix.
In file url.php, function google_seo_url_multipage($url),
Replace:

                if($extra)
                {					
                    $newurl .= $extra;
                }

By:

                if($extra)
                {
					if (str_starts_with($extra, '?') && str_contains($newurl, '?')) {
						$extra = '&' . substr($extra, 1);
					}
					
                    $newurl .= $extra;
                }