How to use multiple parameters in where clause?

I want to make a filter with different parameters. One of parameter is $article_title. But it can be empty . My problem is even if its not empty i get null in return $comments. That is because this part of code:

 $q->where('language_id', $default_language_id)->where('title','like',$article_title);

This is my function

public function getResultCommentsWithArticle($comment,$user_firstname,$article_title,$orderBy){
      $default_language = Languages::where('default',1)->first();
      $default_language_id = $default_language->id;

      $comments = ArticleComments::orderBy($orderBy,'desc')
          ->with(['user', 'article', 'article.translations' => function($q) use($default_language_id,$article_title) {
              $q->where('language_id', $default_language_id)->where('title','like',$article_title);
          }])->paginate(10);
      return $comments;
    }

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