Issue #3352367 by andypost: Fix Variable $graph might not be defined

core/lib/Drupal/Core/Extension/ModuleHandler.php

@@ -230,7 +230,7 @@ class ModuleHandler implements ModuleHandlerInterface {
         }
       }
     }
-    $graph_object = new Graph($graph);
+    $graph_object = new Graph($graph ?? []);
     $graph = $graph_object->searchAndSort();
     foreach ($graph as $module_name => $data) {
       $modules[$module_name]->required_by = $data['reverse_paths'] ?? [];

core/phpstan-baseline.neon

@@ -480,11 +480,6 @@ parameters:
 			count: 1
 			path: lib/Drupal/Core/Extension/ExtensionVersion.php
 
-		-
-			message: "#^Variable \\$graph might not be defined\\.$#"
-			count: 1
-			path: lib/Drupal/Core/Extension/ModuleHandler.php
-
 		-
 			message: "#^Variable \\$callback in isset\\(\\) always exists and is not nullable\\.$#"
 			count: 1