- Quickfix on unexisting SERVER var

src/Kernel.php

@@ -61,7 +61,7 @@ class Kernel {
         Dotenv::create(getenv("PROJECT_PATH"))->load();
 
         // Override using headers
-        if ( ( $keys = getenv('KEYS') ) && ( $auth = $_SERVER["HTTP_X_DEV_AUTH"] ) && in_array($auth, explode(',', $keys)) ) {
+        if ( ( $keys = getenv('KEYS') ) && ( $auth = $_SERVER["HTTP_X_DEV_AUTH"] ?? null ) && in_array($auth, explode(',', $keys)) ) {
             foreach (['APP_ENV', 'DEBUG',] as $env) {
                 if (null !== $value = $_SERVER["HTTP_X_$env"] ?? null) {
                     static::putenv($env, $value);