So I installed SS 4.5.1 using the prefered method (composer) on a local DDEV environment. Everything went fine, no errors, ran dev/build, etc and website is working.
However, logging into the admin it throws the following error everywhere in the pages module. All other modules seem fine and operate without errors.
# [Warning] array_keys() expects parameter 1 to be array, string given
### GET /admin/pages/
Line **926** in **/var/www/html/public_html/vendor/silverstripe/cms/code/Controllers/CMSMain.php**
$context->setSearchParams($params);
$placeholder = _t('SilverStripe\\CMS\\Search\\SearchForm.FILTERLABELTEXT', 'Search') . ' "' .
SiteTree::singleton()->i18n_plural_name() . '"';
$searchParams = $context->getSearchParams();
$searchParams = array_combine(array_map(function ($key) {
return 'Search__' . $key;
}, array_keys($searchParams)), $searchParams);
$schema = [
'formSchemaUrl' => $schemaUrl,
'name' => 'Term',
'placeholder' => $placeholder,
'filters' => $searchParams ?: new \stdClass // stdClass maps to empty json object '{}'