Fix a type hint issue in RouteDescriber

Describer/RouteDescriber.php

@@ -48,7 +48,7 @@ final class RouteDescriber implements DescriberInterface
 
         foreach ($this->routeCollection->all() as $route) {
             // if able to resolve the controller
-            if ($method = $this->getReflectionMethod($route->getDefault('_controller'))) {
+            if ($method = $this->getReflectionMethod($route->getDefault('_controller') ?? '')) {
                 // Extract as many informations as possible about this route
                 foreach ($this->routeDescribers as $describer) {
                     $describer->describe($api, $route, $method);

Tests/Describer/RouteDescriberTest.php

@@ -0,0 +1,47 @@
+<?php
+
+/*
+ * This file is part of the ApiDocBundle package.
+ *
+ * (c) EXSyst
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace EXSyst\Bundle\ApiDocBundle\Tests\Describer;
+
+use EXSyst\Bundle\ApiDocBundle\Describer\RouteDescriber;
+use EXSyst\Bundle\ApiDocBundle\RouteDescriber\RouteDescriberInterface;
+use Symfony\Bundle\FrameworkBundle\Controller\ControllerNameParser;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\Routing\RouteCollection;
+use EXSyst\Component\Swagger\Swagger;
+
+class RouteDescriberTest extends AbstractDescriberTest
+{
+    private $routes;
+    private $routeDescriber;
+
+    public function testIgnoreWhenNoController()
+    {
+        $this->routes->add('foo', new Route('foo'));
+        $this->routeDescriber->expects($this->never())
+            ->method('describe');
+
+        $this->assertEquals((new Swagger())->toArray(), $this->getSwaggerDoc()->toArray());
+    }
+
+    protected function setUp()
+    {
+        $this->routeDescriber = $this->createMock(RouteDescriberInterface::class);
+        $this->routes = new RouteCollection();
+        $this->describer = new RouteDescriber(
+            new Container(),
+            $this->routes,
+            $this->createMock(ControllerNameParser::class),
+            [ $this->routeDescriber ]
+        );
+    }
+}