PHP 8.5 deprecations

[adrianbj]

19× | Deprecated: Using null as an array offset is deprecated, use an empty string instead in .../public_html/site/modules/SearchEngine/lib/Renderer.php:324

1× | Deprecated: Using null as an array offset is deprecated, use an empty string instead in .../public_html/site/modules/SearchEngine/lib/Renderer.php:325

19× | Deprecated: Using null as an array offset is deprecated, use an empty string instead in .../public_html/site/modules/SearchEngine/lib/Renderer.php:330

The fix seems to be to just to initialize $group_name as an empty string instead of null

$group_name = '';

instead of:

$group_name = null;