feat: add null object definition loader

Signed-off-by: Bart Jaskulski <bjaskulski@protonmail.com>

src/Binding/Loader/EmptyDefinitions.php

+<?php
+declare( strict_types=1 );
+
+namespace WPDesk\Init\Binding\Loader;
+
+final class EmptyDefinitions implements BindingDefinitions {
+
+	public function load(): iterable {
+		return [];
+	}
+}

src/Extension/LegacyExtension.php

@@ -6,6 +6,7 @@ namespace WPDesk\Init\Extension;
 
 use Psr\Container\ContainerInterface;
 use WPDesk\Init\Binding\Loader\BindingDefinitions;
+use WPDesk\Init\Binding\Loader\EmptyDefinitions;
 use WPDesk\Init\Configuration\ReadableConfig;
 use WPDesk\Init\DependencyInjection\ContainerBuilder;
 use WPDesk\Init\Plugin\Plugin;
@@ -41,6 +42,6 @@ class LegacyExtension implements Extension {
 	}
 
 	public function bindings( ContainerInterface $c ): BindingDefinitions {
-		return new ArrayBindingLoader( [] );
+		return new EmptyDefinitions();
 	}
 }