Why getFirstMedia returns null?

[4unkur]

I have a strange case where I add a file to Medialibrary and retrieve it via getFirstMedia right after and it returns null when executing for the first time. On the second run, everything is OK.

To reproduce clone the repo:
https://github.com/4unkur/mergepdf

composer install
create DB, set the name in .env file
run php artisan migrate and visit the index page.
You'll see that it dumps the same model, but it returns null for the ->getFirstMedia call on the model.