title: How to fix "Failed prop type: The property `spacing` of `grid` must be used on `container`?
body: <p>I am currently working on a project in which I utilize React and the Material-UI framework. However, after using grid an error pops up saying:</p>
  
  <pre><code>checkPropTypes.js:20 Warning: Failed prop type: The property `spacing` of `Grid` must be used on `container`.
      in WithStyles(ForwardRef(Grid)) (created by NavBar)
      in NavBar (created by Root)
      in Root
  </code></pre>
  
  <p>I have already checked all of my code and the Grid container does use the <code>spacing</code> prop.
  I have also tried removing spacing from Grid item and this causes more errors.</p>
  
  <pre><code>&lt;BrowserRouter&gt;
        &lt;AppBar position="static"&gt;
          &lt;Toolbar style={navStyle}&gt;
            &lt;Grid
              justify="space-between"
              container
              spacing={10}
            &gt;
              &lt;Grid
                item
                spacing={2}
              &gt;
  ...
  </code></pre>
  
  <p>Everything is showing up on the screen properly, however; this error still pops up. I am unsure how to fix this and would love to learn!</p>