flickering subtitle box after subtitles finished

I noticed many times when I am playing a video while its subtitle file has ended, I see a flickering white sub box containing the last subtitle.

Steps to reproduce:
- open a video with a subtitle file that ends sooner than the video.

https://github.com/aidancrowther/ASCIIPlay/assets/71609332/a5ef90ad-7de0-439b-b1e6-39eae5088ca6