Code
T9002 missing-asset
A definition names an asset by a written name, and no file of that name lies under assets/. Every file under assets/ is an asset, named by its path there.
Details
An entry of assets/ that is a link is an asset only where it leads to a file inside assets/. A link that leads to a folder, to nothing, or out of assets/ - to a backend file of the project, to a file that a build made, to a place outside the project - is this code too, and nothing of what it leads to is read into the bundle: a file of the computer never becomes a file that a browser can load because a link points at it.
The fix
Put the file itself into assets/, or name an asset that is there: asset('logo.png') names assets/logo.png.