django中不存在模板错误

{{ update_form }}

part\u detail.html

<div>
<form id="update_form" action="" method="post">
    {% csrf_token %}
    <div id="my_form">
        {% if update_form %}
            {{ update_form }}
        {% else %}
            {% include 'part_stock_form.html' %}
        {% endif %}
    </div>
    <input type="submit" id="btn_stock_update" style="display: none;">
</form>
</div>
  $(function () {

    $('.edit_btn').on('click',pop_up);
    function pop_up() {
        var update_url = url to update stock;
        $('#update_form').attr('action',update_url);
        $("#my_form").load(update_url,function () {
             $("#btn_stock_update").show();
        });
    });
</script>

class stock_update_view(UpdateView):
    model = part_stock
    fields = ['part_id','entry_date','supplier','amount','remaining']
    success_url = reverse_lazy('parts:part_list')
    template_name = 'part_stock_form.html'

    def get_context_data(self, **kwargs):
        context = super(stock_update_view, self).get_context_data(**kwargs)
        context['update_form'] = context.get('form')
        return context

    def form_invalid(self, form):
        print("form is invalid")
        return render(self.request, 'part_details.html', {'update_form': form})

当表单有效时,它工作正常,但当表单无效时,会出现错误