Catch AccountNotFoundException and show 404 page

templates/account_404.html.twig

@@ -0,0 +1,14 @@
+{% extends "base.html.twig" %}
+
+{% block title %}Account not found{% endblock %}
+
+{% block content %}
+    <h2>Account not found</h2>
+
+    <div class="error_box">
+        <h4>Error</h4>
+        <p>The account with the ID {{ id }} was not found.</p>
+    </div>
+
+    <p>Go back to <a href="/accounts">account list</a>.</p>
+{% endblock %}