Closing a card does not automatically unload the video.

[avikalpg]

Steps to reproduce

1. Run the backend and the frontend on your local computer
2. open a card and play the video
3. Close the card without pausing the video -> you will still be able to hear the audio playing in the background.

Desired behaviour

Ideally, the video should be unloaded (and hence, stop playing) as soon as the card unmounts.

If not, at least the previous video should stop playing when another video in a different card is played.