bug #4639 Fix bug in default value (loevgaard)

This PR was merged into the 3.0.x-dev branch.

Discussion
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Fix bug in default value

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Commits
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e1dd9d1 Fix bug in default value

src/Controller/AbstractCrudController.php

@@ -502,7 +502,7 @@ public function renderFilters(AdminContext $context): KeyValueStore
         /** @var FiltersFormType $filtersForm */
         $filtersForm = $this->get(FormFactory::class)->createFiltersForm($filters, $context->getRequest());
         $formActionParts = parse_url($filtersForm->getConfig()->getAction());
-        $queryString = $formActionParts[EA::QUERY] ?? [];
+        $queryString = $formActionParts[EA::QUERY] ?? '';
         parse_str($queryString, $queryStringAsArray);
         unset($queryStringAsArray[EA::FILTERS], $queryStringAsArray[EA::PAGE]);