fix unit test

Author: Roger

app/code/Magento/PageCache/Model/App/Request/Http/IdentifierForSave.php

@@ -60,6 +60,9 @@ public function getValue()
      */
     private function reconstructUrl($url)
     {
+        if (empty($url)) {
+            return [$url, ''];
+        }
         $baseUrl = strtok((string)$url, '?');
         $uri = UriFactory::factory($url);
         $query = $uri->getQueryAsArray();

lib/internal/Magento/Framework/App/PageCache/Identifier.php

@@ -71,6 +71,9 @@ public function getValue()
      */
     private function reconstructUrl($url)
     {
+        if (empty($url)) {
+            return [$url, ''];
+        }
         $baseUrl = strtok((string)$url, '?');
         $uri = UriFactory::factory($url);
         $query = $uri->getQueryAsArray();