Issue #3457179: Make gitlab pipeline green

Closes #3457179

src/Plugin/views/argument/ViewsCsvArgument.php

@@ -42,6 +42,7 @@ class ViewsCsvArgument extends StringArgument {
     }
 
     $this->ensureMyTable();
+    $field = '';
     if (empty($this->options['glossary'])) {
       $field = $this->options['key'];
     }