title: Chart.js: A value is empty, but the line must not be broken
body: <p><a href="https://i.stack.imgur.com/EZgWd.png" rel="nofollow noreferrer">This</a> is a line graph what I want to draw.</p>
  <p>The label is</p>
  <pre><code>[2019, 2020, 2021, 2022]
  </code></pre>
  <p>but the dataset is</p>
  <pre><code>[{
   data: [100, '', 200, 100]
   ...
  }]
  </code></pre>
  <p>The second one in the dataset is null or '', but I want the line not to be broken.</p>
  <p>How can I draw such graph?</p>