minor #1854 [Turbo] Fix TurboExtension for PhpStan (smnandre)

This PR was squashed before being merged into the 2.x branch.

Discussion
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[Turbo] Fix TurboExtension for PhpStan

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Issues        | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT

Commits
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47d9d60 [Turbo] Fix TurboExtension for PhpStan

Author: kbond

src/Turbo/src/DependencyInjection/TurboExtension.php

@@ -114,7 +114,7 @@ private function isAssetMapperAvailable(ContainerBuilder $container): bool
 
         // check that FrameworkBundle 6.3 or higher is installed
         $bundlesMetadata = $container->getParameter('kernel.bundles_metadata');
-        if (!isset($bundlesMetadata['FrameworkBundle'])) {
+        if (!\is_array($bundlesMetadata) || !isset($bundlesMetadata['FrameworkBundle'])) {
             return false;
         }