non-unique slug error message working

public/index.php

@@ -15,6 +15,7 @@ class MyDB extends SQLite3 {
 }
 
 $db = new MyDB();
+ini_set('display_errors', 'Off');
 
 function addNavbar($response)
 {
@@ -85,8 +86,12 @@ $app->map(['GET', 'POST'], '/blog/create', function (Request $request, Response
     if (isset($_SESSION['username'])) {
         if ($request->getMethod() == 'GET') {
             addNavbar($response);
-            $response->getBody()->write($_SESSION['error']);
-            $response->getBody()->write('<hr/>');
+            if ($_SESSION['error']) {
+                $response->getBody()->write($_SESSION['error']);
+                $response->getBody()->write('<hr/>');
+                unset($_SESSION['error']);
+            }
+
             $response->getBody()->write('<form action="/blog/create" method="POST">');
             $response->getBody()->write('<label for="slug">slug:</label>');
             $response->getBody()->write('<input type="text" name="slug"/><br/>');
@@ -95,8 +100,7 @@ $app->map(['GET', 'POST'], '/blog/create', function (Request $request, Response
             $response->getBody()->write('<label for="content">Content:</label>');
             $response->getBody()->write('<textarea name="content" rows="4" columns="50"></textarea>');
             $response->getBody()->write('<input type="submit"/>');
-            addFooter($response);
-            unset($_SESSION['error']);
+            addFooter($response);           
         } else {
             $data = $request->getParsedBody();
             global $db;