Youri van Koppen
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
      /** @var \Drupal\Core\File\FileUrlGeneratorInterface $file_url_generator */
      $file_url_generator = \Drupal::service('file_url_generator');

+      // A dummy query-string is added to filenames, to gain control over
+      // browser-caching. The string changes on every update or full cache
+      // flush, forcing browsers to load a new copy of the files, as the
+      // URL changed.
+      // We need try-catch due to the installer not having a state yet.
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
      /** @var \Drupal\Core\File\FileUrlGeneratorInterface $file_url_generator */
      $file_url_generator = \Drupal::service('file_url_generator');

+      // A dummy query-string is added to filenames, to gain control over
+      // browser-caching. The string changes on every update or full cache
+      // flush, forcing browsers to load a new copy of the files, as the
+      // URL changed.
+      // We need try-catch due to the installer not having a state yet.
+      try {
+        $query_string = \Drupal::service('asset.query_string')->get();
+      }
+      catch (Exception) {
+        $query_string = '0';
+      }