Getting Error when Place Order button on website is clicked

Hi all,
whenever i am clicking on place order button


i am getting an error like this.
but in the system sales order is generated properly.
Why is it giving this error on website any idea?

Traceback (most recent call last):
  File "/home/ghost/frappe-bench/apps/frappe/frappe/website/render.py", line 50, in render
    data = render_page_by_language(path)
  File "/home/ghost/frappe-bench/apps/frappe/frappe/website/render.py", line 177, in render_page_by_language
    return render_page(path)
  File "/home/ghost/frappe-bench/apps/frappe/frappe/website/render.py", line 193, in render_page
    return build(path)
  File "/home/ghost/frappe-bench/apps/frappe/frappe/website/render.py", line 200, in build
    return build_page(path)
  File "/home/ghost/frappe-bench/apps/frappe/frappe/website/render.py", line 223, in build_page
    html = frappe.get_template(context.template).render(context)
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/environment.py", line 1090, in render
    self.environment.handle_exception()
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/environment.py", line 832, in handle_exception
    reraise(*rewrite_traceback_stack(source=source))
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/_compat.py", line 28, in reraise
    raise value.with_traceback(tb)
  File "/home/ghost/frappe-bench/apps/erpnext/erpnext/./templates/pages/order.html", line 2, in top-level template code
    {% from "erpnext/templates/includes/order/order_macros.html" import item_name_and_description %}
  File "/home/ghost/frappe-bench/apps/frappe/frappe/./templates/web.html", line 1, in top-level template code
    {% extends base_template_path %}
  File "/home/ghost/frappe-bench/apps/frappe/frappe/./templates/base.html", line 60, in top-level template code
    </head>
  File "/home/ghost/frappe-bench/apps/frappe/frappe/./templates/web.html", line 56, in block "content"
    <div class="container">
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/sandbox.py", line 462, in call
    return __context.call(__obj, *args, **kwargs)
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/runtime.py", line 679, in _invoke
    rv = self._func(*arguments)
  File "/home/ghost/frappe-bench/apps/frappe/frappe/./templates/web.html", line 15, in template
    {% block page_container %}
  File "/home/ghost/frappe-bench/apps/frappe/frappe/./templates/web.html", line 29, in block "page_container"
    <div class="page_content">
  File "/home/ghost/frappe-bench/apps/erpnext/erpnext/./templates/pages/order.html", line 42, in block "page_content"
    {{ frappe.utils.formatdate(doc.transaction_date, 'medium') }}
  File "/home/ghost/frappe-bench/env/lib/python3.6/site-packages/jinja2/sandbox.py", line 462, in call
    return __context.call(__obj, *args, **kwargs)
TypeError: 'NoneType' object is not callable

Please suggest.