fix: allow empty header name

Author: SMillerDev

src/PHPDraft/Out/OpenAPI/OpenApiRenderer.php

@@ -164,7 +164,7 @@ private function toOperation(HTTPRequest $request, Transition $transition, array
 
         foreach ($request->headers as $name => $value) {
             if ($name === 'Content-Type') { continue; }
-            if ($name === $this->base_data['API_KEY_HEADER']) {
+            if ($name === $this->base_data['API_KEY_HEADER'] ?? NULL) {
                 $operation['security'] = [["api_key" => []]];
                 continue;
             }
@@ -511,4 +511,4 @@ private function getTags(): array {
         return $return;
     }
 
-}
+}