function edit(ClientSite $clientSite) { ... }

What this supposed to mean? ClientSite? Is it a constant? If yes, put comma after it.

It looks like ClientSite is the db model, so this

function edit(ClientSite $clientSite) { ... }

is saying the incoming var $clientSite is suppose to be a instance of the model named ClientSide.

The code isn't updated on the github so I don't see a route that calls edit but I'm going to guess that it or whatever function is calling the edit() function is not passing a instance of the ClientSide model, which is what the function wants.

p.s. Click the link that says how to mark up posts, it makes reading code here so much easier