title: Laravel Excel can't download and export
body: <p>My code is copyed from the website.</p>
  
  <pre><code>Excel::create('Filename', function($excel) {
  
  // Set the title
  $excel-&gt;setTitle('Our new awesome title');
  
  // Chain the setters
  $excel-&gt;setCreator('Maatwebsite')
        -&gt;setCompany('Maatwebsite');
  
    // Call them separately
    $excel-&gt;setDescription('A demonstration to change the file properties');
  })-&gt;download('xls');
  </code></pre>
  
  <p>I successfully download once.</p>
  
  <p>However the other try is error.</p>
  
  <p>The error Message is that.</p>
  
  <pre><code>Whoops, looks like something went wrong.
  
  FatalErrorException in LaravelExcelWriter.php line 263:
  
  
  Call to a member function getMergeCells() on a non-object
  in LaravelExcelWriter.php line 263
  </code></pre>