- Quickfix from error found during PHP 8 migration

src/Dump.php

@@ -26,8 +26,8 @@ class Dump {
     public function renderArray() {
         return [
             'content' => $this->content,
-            'file' => $this->trace['file'],
-            'line' => $this->trace['line'],
+            'file' => $this->trace['file'] ?? '?',
+            'line' => $this->trace['line'] ?? '?',
         ];
     }