Error produced when "goodbye" form added to view

[pauldacus]

In the TUTORIAL.pdf, on page 18-19, the code for a form to delete greetings is as follows:

<form method="post" action="{% url action="goodbye" %}">
Delete:
<select name="greeting_id">
{% for greeting in greetings %}
<option value="{{ greeting.id }}">{{ greeting.greeting_text }}
{% endfor %}
</select>
<input type="submit">
</form>

Putting this form into the list.html template produced an error when you click the "New Greeting" link mentioned earlier in the PDF. The error I got was like this:

Error:
{function_clause,
[{erlydtl_runtime,init_counter_stats,
[undefined,undefined],
[{file,"src/erlydtl_runtime.erl"},{line,208}]},
{cb_test_app_view_greeting_create_html,render_internal,4,[]},
{cb_test_app_view_greeting_create_html,render,2,[]},
{boss_web_controller,render_view,6,
[{file,"src/boss/boss_web_controller.erl"},{line,899}]},
{boss_web_controller,execute_action,5,
[{file,"src/boss/boss_web_controller.erl"},{line,790}]},
{boss_web_controller,process_dynamic_request,5,
[{file,"src/boss/boss_web_controller.erl"},{line,516}]},
{boss_web_controller,process_request,5,
[{file,"src/boss/boss_web_controller.erl"},{line,505}]},
{timer,tc,3,[{file,"timer.erl"},{line,194}]}]}
(Don't worry, this message will not appear in production.)

Oddly, I could see the delete dropdown & submit button, which worked fine, it was only when I clicked on the "New Greeting..." link when I received the above error. Hopefully I am not messing things up somehow, but I did manage to reproduce this same error no matter how I fiddled with this form.