fix 500 error on additional details step

src/registrar/templates/portfolio_domain_request_additional_details.html

@@ -58,7 +58,7 @@
         <div id="anything-else">
             <p><em>This question is optional.</em></p>
             {% with attr_maxlength=2000 add_label_class="usa-sr-only" %}
-                {% input_with_errors forms.0.anything_else %}
+                {% input_with_errors forms.3.anything_else %}
             {% endwith %}
         </div>
     {% endif %}