If you pass a field value to the truncate() filter, like this:
{{ featured_stories[2]['description']|truncate(100, true, '...') }}
and that field is not set, you get a deprecation warning:
> Deprecated function: mb_strlen(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\Component\Utility\Unicode::truncate() (line 310 of core/lib/Drupal/Component/Utility/Unicode.php).
This is because Unicode::truncate() expects its parameter to be a string, and so doesn't check before passing it on to mb_strlen().
Active
3.4
Code
new TwigFilter('truncate', [Unicode::class, 'truncate']),
Twig Tweak is not implementing its own truncate() logic, but is delegating to:
\Drupal\Component\Utility\Unicode::truncate()
we can wrap it in custom method and safely cast or normalize input before it goes into Unicode::truncate().