Twig_File_Filters->check_extension() method : issue when file is non existent (empty upload field in CMS)

[sentry-io]

Sentry Issue: PHP-SURFE-2W

ErrorException: Warning: Trying to access array offset on value of type bool
  File "/wp-content/themes/surfe/lib/twig/file-filters.php", line 42, in Mill3\Twig\Twig_File_Filters::check_extension
    $id = gettype($file) == 'object' ? $file->ID : $file['ID'];
  File "/wp-content/themes/surfe/lib/twig/file-filters.php", line 90, in Mill3\Twig\Twig_File_Filters::is_video
    return $this->check_extension($file, array('mp4'));
  File "/wp-content/plugins/timber-library/lib/Loader.php", line 79, in Timber\Loader::render
    $output = $template->render($data);
  File "/wp-content/plugins/timber-library/lib/Timber.php", line 334, in Timber\Timber::compile
    $output = $loader->render($file, $data, $expires, $cache_mode);
  File "/wp-content/plugins/timber-library/lib/Timber.php", line 383, in Timber\Timber::fetch
    $output = self::compile($filenames, $data, $expires, $cache_mode, true);
...
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