 Class name must be a valid object or a string

On migration it returns
` Class name must be a valid object or a string  \database\migrations\2020_04_22_121205_create_comments_
table.php:35
    31|     private function commentsTable(): string
    32|     {
    33|         $model = config('comment.model');
    34|
   35|         return (new $model)->getTable();
    36|     }
    37| }
`