Fix php engine bug

[ganyicz]

The scenario

Blade crashes when using IDE Helper and running php artisan ide-helper:generate.

The problem

In viewContainsExpiredFrontMatter, we assume the resolved view engine has the getCompiler() method.

However, the IDE Helper renders a php file using the PhpEngine, which doesn't have that method.

$view->getEngine()->getCompiler();

// ❌ Call to undefined method Illuminate\View\Engines\PhpEngine::getCompiler()

This also breaks mails/notifications as Laravel also uses the php engine to render those.

The solution

Do a instanceof CompilerEngine check:

$engine = $view->getEngine();

if (! $engine instanceof CompilerEngine) {
    return false;
}

Fixes #28,#12,#11