Notice: Trying to access array offset on value of type null

Hi,
After switch to PHP 7.4 we have encountered some PHP notices in your plugin:
ErrorException: Notice: Trying to access array offset on value of type null
#18 /wp-content/plugins/contact-form-7/modules/file.php(90): wpcf7_file_validation_filter
#17 /wordpress/wp-includes/class-wp-hook.php(287): WP_Hook::apply_filters
#16 /wordpress/wp-includes/plugin.php(206): apply_filters

And
ErrorException: Notice: Trying to access array offset on value of type null
#18 /wp-content/plugins/contact-form-7/modules/file.php(100): wpcf7_file_validation_filter
#17 /wordpress/wp-includes/class-wp-hook.php(287): WP_Hook::apply_filters

Plugin version: 5.1.9
WP version: 5.4.2
PHP: 7.4

Can you please take a look into this?

Best regards
Maciej