Improve tutorial's voting template to show a message when no choices are available

[Birendra Kumar Sharma]

In the polls tutorial (polls/detail.html), the template currently loops over choices without showing anything if none exist.
This change adds a condition to display a user-friendly message ("No choices available for this question.") when no choices are present.
This improves clarity for beginners and makes the template more informative without altering existing functionality.

[Tim Graham]

I'm not in love with the suggestion, but I'll leave the ticgket open for a second opinion. Tutorial 2 already shows how to add choices to a question, so that proposed section redundant. Tutorial 3 already shows how to use {% if %} / {% else %} to show a "No items available" message. Finally, the patch contains some unneeded indentation changes.

[Sarah Boyce]

I agree with Tim here
I don't see a strong reason why adding more logic makes this clearer. I feel the tutorial should keep logic simple and focus on the concepts it's trying to introduce.
A question is not really "valid" without choices. The detail view also doesn't have an if/else condition. The user of the tutorial can make their own extensions adding logic to handle this

If you disagree, you can bring this up on the forum and add more reasoning: ​https://forum.djangoproject.com/c/internals/5