Can't see subservices on web site

hello everybody
i am trying to show subservices which are under main services group items
but i have this issue for all subservices:
Uncaught Server Exception
Traceback (most recent call last):
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/website/render.py”, line 48, in render
data = render_page_by_language(path)
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/website/render.py”, line 152, in render_page_by_language
return render_page(path)
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/website/render.py”, line 168, in render_page
return build(path)
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/website/render.py”, line 175, in build
return build_page(path)
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/website/render.py”, line 197, in build_page
html = frappe.get_template(context.template).render(context)
File “/home/azahra-erp/frappe-bench/env/lib/python3.5/site-packages/jinja2/environment.py”, line 1008, in render
return self.environment.handle_exception(exc_info, True)
File “/home/azahra-erp/frappe-bench/env/lib/python3.5/site-packages/jinja2/environment.py”, line 780, in handle_exception
reraise(exc_type, exc_value, tb)
File “/home/azahra-erp/frappe-bench/env/lib/python3.5/site-packages/jinja2/_compat.py”, line 37, in reraise
raise value.with_traceback(tb)
File “/home/azahra-erp/frappe-bench/apps/erpnext/erpnext/./templates/generators/item/item.html”, line 1, in top-level template code
{% extends “templates/web.html” %}
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/./templates/web.html”, line 1, in top-level template code
{% extends base_template_path %}
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/./templates/base.html”, line 68, in top-level template code
{% block content %}
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/./templates/web.html”, line 60, in block “content”
{{ main_content() }}
File “/home/azahra-erp/frappe-bench/env/lib/python3.5/site-packages/jinja2/runtime.py”, line 579, in _invoke
rv = self._func(*arguments)
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/./templates/web.html”, line 15, in template
{% block page_container %}
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/./templates/web.html”, line 30, in block “page_container”
{%- block page_content -%}{%- endblock -%}
File “/home/azahra-erp/frappe-bench/apps/erpnext/erpnext/./templates/generators/item/item.html”, line 15, in block “page_content”
{% include “templates/generators/item/item_details.html” %}
File “/home/azahra-erp/frappe-bench/apps/erpnext/erpnext/./templates/generators/item/item_details.html”, line 12, in top-level template code
{% if frappe.utils.strip_html(doc.web_long_description) %}
File “/home/azahra-erp/frappe-bench/apps/frappe/frappe/utils/data.py”, line 607, in strip_html
return _striptags_re.sub("", text)
TypeError: expected string or bytes-like object