Issue #3310666: UpdaterForm throws an exception if you try to update to the next minor beta

src/Form/UpdaterForm.php

@@ -277,24 +277,26 @@ final class UpdaterForm extends FormBase {
       // for it; if we can't, that's an error condition.
       $first_release_version = $next_minor_version->getMajorVersion() . '.' . $next_minor_version->getMinorVersion() . '.0';
       $available_updates = update_get_available(TRUE);
+      $caption = NULL;
       if (isset($available_updates['drupal']['releases'][$first_release_version])) {
         $next_minor_first_release = ProjectRelease::createFromArray($available_updates['drupal']['releases'][$first_release_version]);
-        $form['next_minor'] = $this->createReleaseTable(
-          $next_minor_release,
-          $installed_minor_release ? $this->t('Minor update') : $release_status,
-          $this->t('Latest version of Drupal @major.@minor (next minor) (<a href=":url">Release notes</a>):', [
-            '@major' => $next_minor_version->getMajorVersion(),
-            '@minor' => $next_minor_version->getMinorVersion(),
-            ':url' => $next_minor_first_release->getReleaseUrl(),
-          ]),
-          $installed_minor_release ? 'update-optional' : $type,
-          $create_update_buttons,
-          $is_primary
-        );
+        $caption = $this->t('Latest version of Drupal @major.@minor (next minor) (<a href=":url">Release notes</a>):', [
+          '@major' => $next_minor_version->getMajorVersion(),
+          '@minor' => $next_minor_version->getMinorVersion(),
+          ':url' => $next_minor_first_release->getReleaseUrl(),
+        ]);
       }
       else {
         $this->messenger()->addWarning("Release information for Drupal $first_release_version is not available.");
       }
+      $form['next_minor'] = $this->createReleaseTable(
+        $next_minor_release,
+        $installed_minor_release ? $this->t('Minor update') : $release_status,
+        $caption,
+        $installed_minor_release ? 'update-optional' : $type,
+        $create_update_buttons,
+        $is_primary
+      );
     }
 
     $form['backup'] = [