Attachment system phpBB 3.3.2 broken

[sutrus]

Good day,
On phpbb 3.3.2 / PHP 7.4.13 I have broken attachments.
When I click the button (Add file), I select a file, but none is added.
It does not display any error, but the file does not appear in the list.
Please, you can extend the support for phpbb 3.3 and fix this behavior.
Thank you

[AlexSheer]

Fix
79c7780#diff-11b96a51218c6fa7d68a2a6cb0674575b6a159206c1cbf519fb26364172b34e7R528

[sutrus]

Thank you