bug symfony#58638 [FrameworkBundle] fix null store handling in XML configs (xabbuh)

This PR was merged into the 7.2 branch.

Discussion
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[FrameworkBundle] fix null store handling in XML configs

| Q             | A
| ------------- | ---
| Branch?       | 7.2
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | see symfony#58518
| License       | MIT

Commits
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b50ecb2 fix null store handling in XML configs

Author: nicolas-grekas

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -2028,6 +2028,10 @@ private function registerLockConfiguration(array $config, ContainerBuilder $cont
             // Generate stores
             $storeDefinitions = [];
             foreach ($resourceStores as $resourceStore) {
+                if (null === $resourceStore) {
+                    $resourceStore = 'null';
+                }
+
                 $storeDsn = $container->resolveEnvPlaceholders($resourceStore, null, $usedEnvs);
                 if (!$usedEnvs && !str_contains($resourceStore, ':') && !\in_array($resourceStore, ['flock', 'semaphore', 'in-memory', 'null'], true)) {
                     $resourceStore = new Reference($resourceStore);