Thumbnails sometimes broken

[codedipper]

Example:

https://search.ahwx.org/search.php?q=Italy+losing+the+Euro+Cup+2024&p=0&t=2&nf=1

Reproduce:

1. Apply #169 patch or disable frontends.
2. Make a video search; repeat until you see a result with a missing thumbnail.

Solution: Sometimes /maxresdefault.jpg doesn't return a real thumbnail. A fix is to switch it to /mqdefault.jpg or /default.jpg on line 53 of engines/invidious/video.php, although the resulting thumbnail will be at a lower quality.