Issue #3133604 by Berdir, dww: Dependency compatibility check in system...

Issue #3133604 by Berdir, dww: Dependency compatibility check in system doesn't check if version is defined

(cherry picked from commit 4da7958d)

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

@@ -47,6 +47,7 @@ class ThemeExtensionList extends ExtensionList {
       'comment_user_verification',
     ],
     'screenshot' => 'screenshot.png',
+    'version' => NULL,
     'php' => DRUPAL_MINIMUM_PHP,
     'libraries' => [],
     'libraries_extend' => [],

core/tests/Drupal/KernelTests/Core/Extension/ThemeExtensionListTest.php

@@ -30,4 +30,12 @@ public function testGetlist() {
     $this->assertArrayHasKey('test_theme', $extensions);
   }
 
+  /**
+   * Tests that themes have an empty default version set.
+   */
+  public function testThemeWithoutVersion() {
+    $theme = \Drupal::service('extension.list.theme')->get('test_theme_settings_features');
+    $this->assertNull($theme->info['version']);
+  }
+
 }