Querying nullable BelongsTo through MorphOne

I'm trying to write a code for finding the latest commenter and last commented at properties for a Commentable model.

Those models may or may not have comments, and I'm trying to display them in the index/detail view of Nova.

I tried fetching the latest comment via ->latestOfMany() checking for existence through the ->exists() method, but I'm not sure what to return if the model hasn't been commented yet.

Here's the full trait used:

<?php

namespace App\Traits;

// extension over KirschbaumDevelopment\NovaComments\Commentable
use KirschbaumDevelopment\NovaComments\Commentable;
use KirschbaumDevelopment\NovaComments\Models\Comment;

trait HasComments
{
    use Commentable;

    public function latestComment(): \Illuminate\Database\Eloquent\Relations\MorphOne
    {
        return $this->morphOne(Comment::class, 'commentable')->latestOfMany();
    }

    public function latestCommenter(): ?\Illuminate\Database\Eloquent\Relations\BelongsTo
    {
        $latestComment = $this->morphOne(Comment::class, 'commentable')->latestOfMany();
        if($latestComment->exists()){
            return $latestComment->commenter();
        } else {
            return null; // <-- problematic line
        }
    }

    public function getLastCommentedAtAttribute()
    {
        $latestComment = $this->morphOne(Comment::class, 'commentable')->latestOfMany();
        if($latestComment->exists()){
            return $latestComment->get("created_at");
        } else {
            return null; // <-- problematic line
        }
    }

}

In its current form, called like this:

BelongsTo::make('Last Commenter', 'latestCommenter', User::class)->nullable()

it spits out the following error:

"message": "Call to a member function withoutGlobalScopes() on null",
"exception": "Error",
"file": "<path>/vendor/laravel/nova/src/Fields/BelongsTo.php",
"line": 182

Probably a mild case of RTFM, but I still can't figure it out, or if it's even supported by Nova.