Fix inconsistent return points.

Author: derrabus

Container.php

@@ -276,6 +276,8 @@ private function make(string $id, int $invalidBehavior)
 
             throw new ServiceNotFoundException($id, null, null, $alternatives);
         }
+
+        return null;
     }
 
     /**

ContainerBuilder.php

@@ -592,7 +592,7 @@ private function doGet($id, $invalidBehavior = ContainerInterface::EXCEPTION_ON_
             $definition = $this->getDefinition($id);
         } catch (ServiceNotFoundException $e) {
             if (ContainerInterface::EXCEPTION_ON_INVALID_REFERENCE < $invalidBehavior) {
-                return;
+                return null;
             }
 
             throw $e;

Extension/Extension.php

@@ -101,7 +101,7 @@ public function getConfiguration(array $config, ContainerBuilder $container)
         return null;
     }
 
-    final protected function processConfiguration(ConfigurationInterface $configuration, array $configs)
+    final protected function processConfiguration(ConfigurationInterface $configuration, array $configs): array
     {
         $processor = new Processor();