Laravel rating while creating testimonial - php

Question

I am using this package to get rates from users, which works for products/posts completely fine for me but i have an issue when i don't have exist record in my database!
What I mean?
Normally when you want to rate you will rate to exist record in database such as exist post or exist product and you express yourself about that record by giving start/rates. now i want to use this system for something that doesn't exist such as testimonial means: people write their testimonial and give star then save it, here i get error of
constraint violation: 1048 Column 'rateable_id' cannot be null
and that's simply because this package tries to get id of testimonial while it doesn't exist, so i need a solution to save both together.
my form
<form class="poststars" action="{{route('testimonialsStar')}}" id="addStar" method="POST">
{{ csrf_field() }}
{{Form::label('comment', 'Comment', array('hidden'))}}
{{Form::textarea('comment', null, array('class' => 'form-control'))}}
<span style="padding-top: 20px !important;vertical-align: -moz-middle-with-baseline;padding-left: 4%;color: #fff;">give rate</span>
<input class="star star-5" value="5" id="star-5" type="radio" name="star"/>
<label class="star star-5" for="star-5"></label>
<input class="star star-4" value="4" id="star-4" type="radio" name="star"/>
<label class="star star-4" for="star-4"></label>
<input class="star star-3" value="3" id="star-3" type="radio" name="star"/>
<label class="star star-3" for="star-3"></label>
<input class="star star-2" value="2" id="star-2" type="radio" name="star"/>
<label class="star star-2" for="star-2"></label>
<input class="star star-1" value="1" id="star-1" type="radio" name="star"/>
<label class="star star-1" for="star-1"></label>
<button type="submit" class="btn btn-success" name="submit">Send</button>
</form>
My routes
//Testimonial Rating System
Route::post('/ratingtes', 'IndexController#testimonialsStar')->name('testimonialsStar');
Route::get('/writetestimonials', 'IndexController#testimonialsds')->name('testimonialsindex');
My Methods
public function testimonialsStar (Request $request, Testimonial $testimonial) {
$rating = new Rating;
$rating->user_id = \Auth::id();
$rating->rating = $request->input('star');
$rating->comment = $request->input('comment');
$rating->rateable_id = str_random(40);
$testimonial->ratings()->save($rating);
return redirect()->back();
}
public function testimonialsds () {
return view('frontend.testimonials');
}
Thanks.