title: react-latex fraction line doesn't display
body: <p>I'm developing a React PWA using Latex to display math equations.  Most equations display perfectly, but the division line is missing in fractions. The component imports react-latex 1.6.0 and katex.min.css is cached. </p>
  
  <p>The division line is missing in Chrome, Safari and Xcode simulator.   </p>
  
  <p>Here's the React/JSX code in a stateless functional component:</p>
  
  <pre><code>let a = 5;
  let b = 6;
  const fraction = `$$\\huge\\frac{${a}}{${b}} \\times \\frac{4}{11} = ?$$`;
  &lt;h3&gt;
  Multiply fractions:
  &lt;/h3&gt;   
  &lt;Latex displayMode={true}&gt;{fraction}&lt;/Latex&gt;
  </code></pre>
  
  <p>Output: 
  <a href="https://i.stack.imgur.com/zcw6o.png" rel="nofollow noreferrer">fraction display example</a></p>
  
  <p>Any suggestions would be appreciated.  </p>