Edit uploaded image with Intervention

I am adding the ability to edit an image that is already uploaded on a shopping cart app I am building. I am able to upload an image fine. I am also able to edit every field perfectly except for the image file upload.

I have tried using the same code I have in the upload function to basically upload another image over the existing one but it does not work and throws an error

Call to a member function getClientOriginalExtension() on a non-object

I am using the Laravel framework with intervention and went to the main site of intervention and it does not show an update or edit method. It just shows a delete method.

I need some help in figuring out how to update the image in my postEdit function.

I really have tried everything I know and have researched this with google and cannot figure this out.

My problem lies in this line of code:

File::update('public/'.$product->image);

Thank you for the right direction.

Here is the image upload function (which works perfect)

public function postCreate() {
    $validator = Validator::make(Input::all(), Product::$rules);

    if ($validator->passes()) {
        $product = new Product;
        $product->category_id = Input::get('category_id');
        $product->title = Input::get('title');
        $product->description = Input::get('description');
        $product->price = Input::get('price');

        $image = Input::file('image');
        $filename  = time() . '.' . $image->getClientOriginalExtension();
        $path = public_path('img/products/' . $filename);
        Image::make($image->getRealPath())->resize(468, 249)->save($path);
        $product->image = 'img/products/'.$filename;
        $product->save();

        return Redirect::to('admin/products/index')
            ->with('message', 'Product Created');
    }

    return Redirect::to('admin/products/index')
        ->with('message', 'Something went wrong')
        ->withErrors($validator)
        ->withInput();
}

Here is the edit image upload function which I cannot get to work.

public function postEdit() {
    $product = Product::find(Input::get('id'));


    if ($product) {
        File::update('public/'.$product->image);
        $product->update(Input::all());
        return Redirect::to('admin/products/index')
        ->with('message', 'Product Updated');
    }

    return Redirect::to('admin/products/index')
        ->with('message', 'Something went wrong, please try again');
}