[13.x] Fix HandleExceptions fatal when static::$app is null during Octane request marshaling

[majidfeiz]

Problem

When using Laravel Octane with FrankenPHP and symfony/http-foundation 8.1, all JSON requests return empty HTTP 500 responses with no logged errors.

Root cause (two combined bugs):

1. Symfony 8.1 added PHP 8.4 property set hooks on Request::$request and other public properties that fire E_USER_DEPRECATED on direct assignment. FrankenPHP's marshalRequest() assigns to this property during request setup — before the Octane sandbox app is fully initialized.

2. When the deprecation fires, HandleExceptions::shouldIgnoreDeprecationErrors() calls static::$app->hasBeenBootstrapped() — but in Octane's transitional state, static::$app can be null, causing a fatal "Call to member function on null", which results in a silent empty HTTP 500.

Fix

Add a null guard before calling any method on static::$app:

protected function shouldIgnoreDeprecationErrors()
{
    return ! class_exists(LogManager::class)
        || is_null(static::$app)    // ← added
        || ! static::$app->hasBeenBootstrapped()
        || ...;
}

Why it doesn't break existing features

• The check short-circuits only when $app is null — a state where logging deprecations is impossible anyway.
• All 17 existing HandleExceptionsTest tests pass unchanged.
• Existing behavior for normal (non-Octane) apps is completely unaffected.

Benefit to end users

Octane + FrankenPHP users running symfony/http-foundation 8.1 can send JSON requests without getting silent HTTP 500 errors.

Closes #60365