[SOLVED] Update problem with foreign key

Hi community.

During the development of a project I get an error which I cannot solve.

The error message is:
_______________________________________________________________
mysqli_sql_exeption #1452
Cannot add or update a child row: a foreign key constraint fails
____________________________________________________________________

The associated controller function:

PHP Code:

public function update($id)
    {
        $homegame = $this->getHomegameOr404($id);

        $post = $this->request->getPost();

        unset($post['user_id']);

        $homegame->fill($post);

        if(! $homegame->hasChanged()){
            
            return redirect()->back()
                             ->with('warning',lang('App.messages.noupdate'))
                             ->withInput();
        }
        
        if($this->homegame_model->save($homegame)) {

            return redirect()->to("/homegames/show/$id")
                             ->with('info', lang('App.messages.homegame_edited'));
        } else {
            return redirect()->back()
                             ->with('errors', $this->homegame_model->errors())
                             ->with('warning', lang('App.messages.invalid'))
                             ->withInput();
        }
    } 


The associated tables: (as images)
HOMEGAMES


USERS


How to solve this error ? Any hints ?

Greetings

Kigh...