BUGFIX: SiteDetectionMiddleware should not crash without doctrine migrations

[mhsdesign]

The SiteDetectionMiddleware tries to match the current requested host to a site entity. For that our doctrine repositories are required. But in the case doctrine is not setup (migrated or no database exists) this middleware should not throw!

Especially non neos routes must still work as the site detection stuff is only mandatory for neos escr things.

Additional fix for #4446

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• Code follows the PSR-2 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[kitsunet]

This seems so overly complicated somehow, doesn#t it boil down to:

try { <stuff to find site> } catch {site = null} 
if ($site instanceof Site) {
    $siteDetectionResult = SiteDetectionResult::create($site->getNodeName(), $site->getConfiguration()->contentRepositoryId);
    $request = $siteDetectionResult->storeInRequest($request)
}

return $handler->handle($request);

[kitsunet]

I would also catch this silently here I guess? but that's srely debatable, I don't think this is the right place to explode about it though.