Trying to save a polymorphic relationship yields ErrorException

[zakiaziz]

The error I'm receiving:

ErrorException in Ardent.php line 821:
Invalid argument supplied for foreach()

Models:

class ModelOne extends Ardent
{
    public function modelThree()
    {
        return $this->morphToMany('App\ModelThree', 'modelthreeable');
    }
}

class ModelTwo extends Ardent
{
    public function modelThree()
    {
        return $this->morphToMany('App\ModelThree', 'modelthreeable');
    }   

}

class ModelThree extends Ardent
{
    public function modelOne()
    {
        return $this->morphedByMany('App\ModelOne', 'modelthreeable');
    }

    public function modelTwo()
    {
        return $this->morphedByMany('App\ModelTwo', 'modelthreeable');
    } 
}

Controller:

class ModelThreeController extends Controller
{
    public function store(Request $request)
    {
        $modelThree = new modelThree;
        $modelThree->name = $request->input('amount', NULL);

        $modelOne = App\ModelOne::find($modelOneId);
        $modelOne->modelThree()->save($modelThree);
    }
}

(I'm aware in the code above ModelTwo is not being touched)