Laravel显示：“unserialize（）：当表列为空时，错误在6字节的偏移0处”

I have a table(books) with column named(genre) with serialize array.

when I show the page using

public function show($id)
{
    $books = Book::findOrFail($id);
    return view('books.show')->with('books', $books);
}

if the table column has array it will display the data. if the column is empty it should display "empty" but whenever the column is empty it will throw error "unserialize(): Error at offset 0 of 6 bytes".

 @if(!empty($books->genre))
     <dt class="font-weight-bold">Genre:</dt>
         <dd>-
             @foreach (unserialize($books->genre) as $item)
                  <span class="pr-3">{{ $item }}</span>
             @endforeach
         </dd>
  @else
       <h1>Empty</h1>
  @endif

I also have trie using isset() and is_array() instead of !empty() and still it failed.