title: React-admin MenuItemLink onClick not working
body: <p>I've got react-admin v3 running very smoothly, but I'm struggling with one point.</p>
  
  <p>I've got a custom user menu component set up as below, but the handleClick event isn't called at all - nothing in the console, and no window opening. Instead, the browser navigates to /billing</p>
  
  <pre><code>render() {
          const { crudGetOne, profile, ...props } = this.props;
  
          const handleClick = (e) =&gt; {
              e.preventDefault();
              e.stopPropagation();
              console.log("In usermenu handleClick");
              console.log("Opening window to {process.env.REACT_APP_BILLING_URL}");
              window.open("{process.env.REACT_APP_BILLING_URL}", '_blank');
  
          }
  
          return (
              &lt;UserMenu {...props}&gt;
                  &lt;MenuItemLink
                      to="/profile"
                      primaryText="Profile"
                      leftIcon={&lt;AccountCircleIcon /&gt;}
                  /&gt;
                  &lt;MenuItemLink
                      to="/billing"
                      primaryText="Billing"
                      leftIcon={&lt;PaymentIcon /&gt;}
                      onClick={handleClick}
                      component={Link}
                  &gt;Billing&lt;/MenuItemLink&gt;
              &lt;/UserMenu&gt;
          );
      }
  </code></pre>
  
  <p>If anyone can help, or suggest another way to have an external link open from the menuitem, that would be fantastic, it's been bugging me for ages. And amazingly, I can't find anyone else asking the same question.</p>
  
  <p>Regards,
  Andy</p>