fix tests too

Author: garak

tests/Provider/BuilderAliasProviderTest.php

@@ -44,7 +44,7 @@ public function testGetExistentMenu(): void
 
     public function testGetContainerAwareMenu(): void
     {
-        if (!interface_exists(ContainerAwareInterface::class)) {
+        if (!\interface_exists(ContainerAwareInterface::class)) {
             self::markTestSkipped('missing interface');
         }
         $item = $this->getMockBuilder('Knp\Menu\ItemInterface')->getMock();

tests/Stubs/Menu/ContainerAwareBuilder.php

@@ -11,7 +11,7 @@ class ContainerAwareBuilder implements ContainerAwareInterface
 {
     private ContainerInterface $container;
 
-    public function setContainer(ContainerInterface $container = null): void
+    public function setContainer(?ContainerInterface $container = null): void
     {
         $this->container = $container;
     }