Resolve #3458435 "Deprecated strpos passing"

Closes #3458435

src/PrettyPathsActiveFilters.php

@@ -228,7 +228,7 @@ class PrettyPathsActiveFilters {
 
     // For views data export with batch, retrieve filters from the batch source
     // URL, defined as GET parameter.
-    if (strpos($this->routeMatch->getRouteName(), 'system.batch_page') === 0) {
+    if (strpos(($this->routeMatch->getRouteName() ?? ''), 'system.batch_page') === 0) {
       $batch_id = $this->request->query->get('id');
       $batch_set = $this->batchStorage->load($batch_id);
       if (!empty($batch_set['source_url'])) {