ACP2E-3467: [Cloud] 500 response to empty Graphql response on 2.4.7

Author: dhorytskyi

app/code/Magento/GraphQl/Controller/GraphQl.php

@@ -7,6 +7,8 @@
 
 namespace Magento\GraphQl\Controller;
 
+use GraphQL\Error\FormattedError;
+use GraphQL\Error\SyntaxError;
 use Magento\Framework\App\Area;
 use Magento\Framework\App\AreaList;
 use Magento\Framework\App\FrontControllerInterface;
@@ -206,6 +208,11 @@ public function dispatch(RequestInterface $request): ResponseInterface
                 );
                 $statusCode = 200;
             }
+        } catch (SyntaxError $error) {
+            $result = [
+                'errors' => [FormattedError::createFromException($error)],
+            ];
+            $statusCode = 400;
         } catch (\Exception $error) {
             $result = [
                 'errors' => [$this->graphQlError->create($error)],

dev/tests/integration/testsuite/Magento/GraphQl/Controller/GraphQlControllerTest.php

@@ -272,4 +272,14 @@ public function testDispatchWithOptions(): void
         self::assertEquals(204, $response->getStatusCode());
         self::assertEmpty($response->getContent());
     }
+
+    public function testDispatchWithoutQuery(): void
+    {
+        $this->request->setPathInfo('/graphql');
+        $this->request->setMethod('GET');
+        $response = $this->graphql->dispatch($this->request);
+        self::assertEquals(400, $response->getStatusCode());
+        $output = $this->jsonSerializer->unserialize($response->getContent());
+        self::assertNotEmpty($output['errors']);
+    }
 }