Issue #3236789 by alexpott: Drupal\Core\Controller\TitleResolver::getTitle()...

Issue #3236789 by alexpott: Drupal\Core\Controller\TitleResolver::getTitle() can result in PHP 8.1 deprecation notices due to NULL being set as placeholder values

core/lib/Drupal/Core/Controller/TitleResolver.php

@@ -65,8 +65,8 @@ public function getTitle(Request $request, Route $route) {
       $args = [];
       if (($raw_parameters = $request->attributes->get('_raw_variables'))) {
         foreach ($raw_parameters->all() as $key => $value) {
-          $args['@' . $key] = $value;
-          $args['%' . $key] = $value;
+          $args['@' . $key] = $value ?? '';
+          $args['%' . $key] = $value ?? '';
         }
       }
       if ($title_arguments = $route->getDefault('_title_arguments')) {

core/tests/Drupal/Tests/Core/Controller/TitleResolverTest.php

@@ -102,6 +102,24 @@ public function providerTestStaticTitleWithParameter() {
     ];
   }
 
+  /**
+   * Tests a static title with a NULL value parameter.
+   *
+   * @see \Drupal\Core\Controller\TitleResolver::getTitle()
+   */
+  public function testStaticTitleWithNullValueParameter() {
+    $raw_variables = new ParameterBag(['test' => NULL, 'test2' => 'value']);
+    $request = new Request();
+    $request->attributes->set('_raw_variables', $raw_variables);
+
+    $route = new Route('/test-route', ['_title' => 'static title %test @test']);
+    $translatable_markup = $this->titleResolver->getTitle($request, $route);
+    $this->assertSame('', $translatable_markup->getArguments()['@test']);
+    $this->assertSame('', $translatable_markup->getArguments()['%test']);
+    $this->assertSame('value', $translatable_markup->getArguments()['@test2']);
+    $this->assertSame('value', $translatable_markup->getArguments()['%test2']);
+  }
+
   /**
    * Tests a dynamic title.
    *