Trim() deprecated warning in vertical-teaser.tpl.php

Seeing a lot of this after the upgrade to PHP8.1

Deprecated function: trim(): Passing null to parameter #1 ($string) of type string is deprecated in include() (line 21 of /var/aegir/platforms/drupal-7-2.9-staging/profiles/cambridge/modules/features/cambridge_teasers/templates/node----vertical-teaser.tpl.php).