Just a quick fix, the logo wasn't displaying correctly I probably should do this with a separate CSS file for all images, but I just did this quick and dirty with a style attribute
As part of the new logo (https://github.com/JulianPrieber/littlelink-custom/milestone/1) I'm now using the new 'logo.svg' vector logo.
For this, I added an if-else statement in most cases, which first check for a custom logo uploaded by the admin or the avatar of an individual user. If the image doesn't exist, the default logo (logo.svg) is used.