Laravel Trying to get property id of non-object

I am trying to update variables at About Us table, but i am getting this error. What is wrong?

AboutUsController:

   /**
     * Show the form for editing the specified resource.
     *
     * @param  AppModelsAboutUs $aboutUs
     * @return IlluminateHttpResponse
     */
    public function edit($aboutUs_id)
    {
        $aboutUs = AboutUs::find($aboutUs_id);
        return view('auth.aboutus.form',compact('aboutUs'));
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  IlluminateHttpRequest  $request
     * @param  AppModelsAboutUs $aboutUs
     * @return IlluminateHttpResponse
     */
    public function update(AboutUsRequest $request, AboutUs $aboutUs)
    {
        $params = $request->all();

        $aboutUs->update($request->all($params));

        return redirect()->route('aboutUs.index')->with('success','Post updated successfully');
    }

Here is my AboutUsRequest, where i am getting this error:

    public function rules()
    {
        $rules = [
            'title1' => 'required|min:5',
            'body1' => 'required|min:5',
        ];

        if ($this->route()->named('aboutUs.update')) {
            $rules['title1'] .= ',' . $this->route()->parameter('aboutUs')->id;
        }

        return $rules;
    }
}