I have tested this item ✅ successfully on 834b5af

Look in frontend in PHP 8.1 with all errors on and Joomla debug on, while finder is re-indexing.

Do you have a stack trace here so we know where the "null" value is comming from? As the signature clearly says "The query input string."

And can you tell me what re-indexing you mean and how to trigger that in the frontend? Isnt indexing triggerd by the backend? Maybe I'm missing something here?

Look in frontend in PHP 8.1 with all errors on and Joomla debug on, while finder is re-indexing.

Do you have a stack trace here so we know where the "null" value is comming from? As the signature clearly says "The query input string."

Hi @zero-24,
Sure!

Call Stack

1 | 0.0001 | 364872 | {main}(  ) | .../index.php:0
2 | 0.0150 | 938704 | Joomla\CMS\Application\CMSApplication->execute(  ) | .../index.php:49
3 | 0.1223 | 3580104 | Joomla\CMS\Application\SiteApplication->render(  ) | .../CMSApplication.php:231
4 | 0.1224 | 3580208 | Joomla\CMS\Application\CMSApplication->render(  ) | .../SiteApplication.php:778
5 | 0.1275 | 3640504 | Joomla\CMS\Document\HtmlDocument->render( $caching = FALSE, $params = ['template'  => 'protostar', 'file' => 'index.php', 'params' => class  Joomla\Registry\Registry { protected $data = class stdClass { ... };  protected $initialized = TRUE; public $separator = '.' }, 'directory'  => '/home/beat/www/j/templates'] ) | .../CMSApplication.php:1140
6 | 0.1275 | 3640504 | Joomla\CMS\Document\HtmlDocument->_renderTemplate(  ) | .../HtmlDocument.php:577
7 | 0.1281 | 3642808 | Joomla\CMS\Document\HtmlDocument->getBuffer( $type = 'modules', $name = 'position-7', $attribs = ['name' => 'position-7', 'style' => 'well'] ) | .../HtmlDocument.php:803
8 | 0.1281 | 3642888 | Joomla\CMS\Document\Renderer\Html\ModulesRenderer->render( $position = 'position-7', $params = ['name' => 'position-7', 'style' => 'well'], $content = NULL ) | .../HtmlDocument.php:511
9 | 0.3278 | 6192000 | Joomla\CMS\Document\Renderer\Html\ModuleRenderer->render( $module = class  stdClass { public $id = '84'; public $title = 'Smart Search Module';  public $module = 'mod_finder'; public $position = 'position-7'; public  $content = ''; public $showtitle = '1'; public $params =  '{"searchfilter":"","show_autosuggest":"1","show_advanced":"0","field_size":20,"show_label":"0","label_pos":"top","alt_label":"","show_button":"0","button_pos":"right","opensearch":"1","opensearch_title":"","set_itemid":"0","layout":"_:default","moduleclass_sfx":"","module_tag":"div","bootstrap_size":"0","header_tag":"h3","header_class":"","style":"0"}';  public $menuid = '0'; public $name = 'finder'; public $style = NULL }, $attribs = ['name' => 'position-7', 'style' => 'well'], $content = NULL ) | .../ModulesRenderer.php:47
10 | 0.3278 | 6194656 | Joomla\CMS\Helper\ModuleHelper::renderModule( $module = class  stdClass { public $id = '84'; public $title = 'Smart Search Module';  public $module = 'mod_finder'; public $position = 'position-7'; public  $content = ''; public $showtitle = '1'; public $params =  '{"searchfilter":"","show_autosuggest":"1","show_advanced":"0","field_size":20,"show_label":"0","label_pos":"top","alt_label":"","show_button":"0","button_pos":"right","opensearch":"1","opensearch_title":"","set_itemid":"0","layout":"_:default","moduleclass_sfx":"","module_tag":"div","bootstrap_size":"0","header_tag":"h3","header_class":"","style":"0"}';  public $menuid = '0'; public $name = 'finder'; public $style = NULL }, $attribs = ['name' => 'position-7', 'style' => 'well'] ) | .../ModuleRenderer.php:98
11 | 0.3281 | 6221760 | include( '/home/beat/www/j/modules/mod_finder/mod_finder.php ) | .../ModuleHelper.php:200
12 | 0.3318 | 6246464 | ModFinderHelper::getQuery( $params = class  Joomla\Registry\Registry { protected $data = class stdClass { public  $searchfilter = ''; public $show_autosuggest = '1'; public  $show_advanced = '0'; public $field_size = 20; public $show_label = '0';  public $label_pos = 'top'; public $alt_label = ''; public $show_button =  '0'; public $button_pos = 'right'; public $opensearch = '1'; public  $opensearch_title = ''; public $set_itemid = '0'; public $layout =  '_:default'; public $moduleclass_sfx = ''; public $module_tag = 'div';  public $bootstrap_size = '0'; public $header_tag = 'h3'; public  $header_class = ''; public $style = '0' }; protected $initialized =  TRUE; public $separator = '.' } ) | .../mod_finder.php:54
13 | 0.3398 | 6249616 | FinderIndexerQuery->__construct( $options = ['filter' => 0, 'filters' => [0 => 0]] ) | .../helper.php:84
14 | 0.3399 | 6253064 | FinderIndexerQuery->processString( $input = NULL, $lang = 'en', $mode = 'AND' ) | .../query.php:236
15 | 0.3399 | 6253064 | html_entity_decode( $string = NULL, $flags = 3, $encoding = 'UTF-8' )

And can you tell me what re-indexing you mean and how to trigger that in the frontend? Isnt indexing triggerd by the backend? Maybe I'm missing something here?

The error appears in the Smart Search module like this:

Please check: https://github.com/joomla/joomla-cms/blob/3.10-dev/administrator/components/com_finder/helpers/indexer/query.php#L175

and update it to $this->input = isset($options['input']) ? $options['input'] : '';

That should do the trick too.

Please check: https://github.com/joomla/joomla-cms/blob/3.10-dev/administrator/components/com_finder/helpers/indexer/query.php#L175

and update it to $this->input = isset($options['input']) ? $options['input'] : '';

That should do the trick too.

Yes, it fixes it too, and as it's better typed, it's a better fix too. Thank you! Updated the PR, with mention in the commit message..

Thanks merging it here :)