Issue #3260248 by Barry_Fisher: BlockViewBuilder error prevents cron from running when called from CLI

src/View/BlockViewBuilder.php

@@ -121,10 +121,15 @@ class BlockViewBuilder {
     if ($access->isAllowed()) {
       // Title block needs a special treatment.
       if ($block_plugin instanceof TitleBlockPluginInterface) {
+        // Account for the scenario that a NullRouteMatch is returned. This, for
+        // example, is the case when Search API is indexing the site during
+        // Drush cron.
+        if ($route = $this->routeMatch->getRouteObject()) {
           $request = $this->requestStack->getCurrentRequest();
-        $title = $this->titleResolver->getTitle($request, $this->routeMatch->getRouteObject());
+          $title = $this->titleResolver->getTitle($request, $route);
           $block_plugin->setTitle($title);
         }
+      }
 
       // Place the content returned by the block plugin into a 'content' child
       // element, as a way to allow the plugin to have complete control of its