title: Props are undefined in react when passing through <Route/>
body: <p>My props are undnefined in react. Here's my app.js line of code:</p>
  
  <pre><code>&lt;Route
              exact
              path='/solutions/standard'
              category={'standard'}
              component={Solutions}
            /&gt;
  </code></pre>
  
  <p>and here is my componenet:</p>
  
  <pre><code>import React from 'react';
  import { Helmet } from 'react-helmet';
  
  const Solutions = ({category}) =&gt; {
      const pageTitle = `${
        category.substring(0, 1).toUpperCase() + category.substring(1)
      } Solutions`;
    return (
      &lt;div&gt;
        &lt;Helmet&gt;
          &lt;title&gt;{pageTitle}&lt;/title&gt;
        &lt;/Helmet&gt;
      &lt;/div&gt;
    );
  };
  
  export default Solutions;
  </code></pre>
  
  <p>but I get this as a render error:</p>
  
  <pre><code>TypeError: Cannot read property 'substring' of undefined
  </code></pre>
  
  <p>Basically the category prop is undefined for whatever reason. </p>