title: Alert keeps staying even after reload
body: <p>Express:</p>
  
  <pre><code>router.get('/polls/new', isLoggedIn, (req, res) =&gt; {
      res.render('new', {title: 'Create a new poll', route: 'new', isLoggedIn: req.isAuthenticated(), errors: req.session.errors});
      req.session.errors = null;
  });
  
  router.post('/polls', isLoggedIn, (req, res) =&gt; {
      req.check('title', 'Title must contain atleast 10 characters and must not exceed 100 charcters').isLength({min: 10, max: 100});
      var errors = req.validationErrors();
      console.log(errors);
      if (errors) {
          req.session.errors = errors;
          res.redirect('/polls/new');
      }
  </code></pre>
  
  <p>EJS:</p>
  
  <pre><code>&lt;% if (errors)  { %&gt;
  &lt;% errors.forEach((error) =&gt; { %&gt;
      &lt;div class="alert alert-danger alert-dismissible fade show" role="alert"&gt;
        &lt;button type="button" class="close alert-dismissible" data-dismiss="alert" aria-label="Close"&gt;
          &lt;span aria-hidden="true"&gt;&amp;times;&lt;/span&gt;
        &lt;/button&gt;
        &lt;strong&gt;Error!&lt;/strong&gt; &lt;%= error.msg %&gt;
      &lt;/div&gt;
  &lt;% }); } %&gt;
  </code></pre>
  
  <p>Am trying to show alert messages when the validation fails. It works perfectly fine. But when the page is reloaded the alert message still shows up even if I made the errors null. </p>