Sales order printing problem

[RamiTHelal]

Dear Experts,
I got this error while I'm trying to print a sales order.
Please help with you experience...

Odoo Server Error

Traceback (most recent call last):
File "/opt/odoo/odoo-server/addons/report/controllers/main.py", line 121, in report_download
response = self.report_routes(reportname, docids=docids, converter='pdf')
File "/opt/odoo/odoo-server/openerp/http.py", line 396, in response_wrap
response = f(_args, *_kw)
File "/opt/odoo/odoo-server/addons/report/controllers/main.py", line 65, in report_routes
pdf = report_obj.get_pdf(cr, uid, docids, reportname, data=options_data, context=context)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/addons/report/models/report.py", line 190, in get_pdf
html = self.get_html(cr, uid, ids, report_name, data=data, context=context)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/addons/report/models/report.py", line 175, in get_html
return self.render(cr, uid, [], report.report_name, docargs, context=context)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/addons/report/models/report.py", line 151, in render
return view_obj.render(cr, uid, template, values, context=context)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 1015, in render
return self.pool[engine].render(cr, uid, id_or_xml_id, qcontext, loader=loader, context=context)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 253, in render
return self.render_node(self.get_template(id_or_xml_id, qwebcontext), qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 294, in render_node
result = self.render_element(element, template_attributes, generated_attributes, qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 315, in render_element
g_inner.append(self.render_node(current_node, qwebcontext))
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 292, in render_node
result = self._render_tag[t_render](self, element, template_attributes, generated_attributes, qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 439, in render_tag_call
return self.render(cr, uid, template, d)
File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
return old_api(self, _args, *_kwargs)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 253, in render
return self.render_node(self.get_template(id_or_xml_id, qwebcontext), qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 294, in render_node
result = self.render_element(element, template_attributes, generated_attributes, qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 315, in render_element
g_inner.append(self.render_node(current_node, qwebcontext))
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 292, in render_node
result = self._render_tag[t_render](self, element, template_attributes, generated_attributes, qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 458, in render_tag_set
qwebcontext[template_attributes["set"]] = self.eval_object(template_attributes["value"], qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 200, in eval_object
return self.eval(expr, qwebcontext)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 197, in eval
raise_qweb_exception(message="Could not evaluate expression %r" % expr, expression=expr, template=template)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 194, in eval
return qwebcontext.safe_eval(expr)
File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_qweb.py", line 80, in safe_eval
return eval(expr, None, locals_dict, nocopy=True, locals_builtins=True)
File "/opt/odoo/odoo-server/openerp/tools/safe_eval.py", line 314, in safe_eval
return eval(c, globals_dict, locals_dict)
File "", line 1, in
QWebException: "cannot concatenate 'str' and 'NoneType' objects" while evaluating
"'container '+lang_direction"