Laravel Empty Password hashing

When I trying to update user data and let The Password Field empty it hashed again that means the password will change and you can't log in again so is there any way to fix this problem ??

Code

$this->validate($request, [
        'first_name'=> 'required|string',
        'last_name' =>  'required|string',
        'email'     =>  'required|email|unique:users,email,'.Auth::id(),
        'password'  =>  'sometimes|nullable|string|min:8,'.Auth::id(),
        'avatar'    =>  'image|mimes:jpg,jpeg,gif,png,svg|max:2048,'.Auth::id(),
        'gender'    =>  'required',
        'country_id'=>  'required',
    ]);

    $user = User::find(Auth::id());

    $user->first_name = $request->first_name;
    $user->last_name = $request->last_name;
    $user->email = $request->email;
    $user->gender = $request->gender;
    $user->country_id = $request->country_id;
    $user->password = bcrypt(request('password'));
    if($request->hasFile('avatar')){
        $avatar = $request->file('avatar');
        $filename = time() . '.' . $avatar->getClientOriginalExtension();
        Image::make($avatar)->resize(300, 300)->save( public_path('/images/avatars/' . $filename ) );
        $user->avatar = $filename;
    }

    $user->save();

    return redirect()->back();

via Chebli Mohamed