Pos Smart Dashboard

Traceback (most recent call last):
  File "/odoo/odoo-server/odoo/http.py", line 642, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/odoo/odoo-server/odoo/http.py", line 684, in dispatch
    result = self._call_function(**self.params)
  File "/odoo/odoo-server/odoo/http.py", line 334, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/odoo/odoo-server/odoo/service/model.py", line 101, in wrapper
    return f(dbname, *args, **kwargs)
  File "/odoo/odoo-server/odoo/http.py", line 327, in checked_call
    result = self.endpoint(*a, **kw)
  File "/odoo/odoo-server/odoo/http.py", line 942, in __call__
    return self.method(*args, **kw)
  File "/odoo/odoo-server/odoo/http.py", line 507, in response_wrap
    response = f(*args, **kw)
  File "/odoo/odoo-server/addons/web/controllers/main.py", line 899, in call_button
    action = self._call_kw(model, method, args, {})
  File "/odoo/odoo-server/addons/web/controllers/main.py", line 887, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/odoo/odoo-server/odoo/api.py", line 689, in call_kw
    return call_kw_multi(method, model, args, kwargs)
  File "/odoo/odoo-server/odoo/api.py", line 680, in call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/odoo/odoo-server/odoo/addons/base/module/module.py", line 413, in button_immediate_install
    return self._button_immediate_function(type(self).button_install)
  File "/odoo/odoo-server/odoo/addons/base/module/module.py", line 495, in _button_immediate_function
    modules.registry.Registry.new(self._cr.dbname, update_module=True)
  File "/odoo/odoo-server/odoo/modules/registry.py", line 83, in new
    odoo.modules.load_modules(registry._db, force_demo, status, update_module)
  File "/odoo/odoo-server/odoo/modules/loading.py", line 377, in load_modules
    loaded_modules, update_module, models_to_check)
  File "/odoo/odoo-server/odoo/modules/loading.py", line 270, in load_marked_modules
    perform_checks=perform_checks, models_to_check=models_to_check
  File "/odoo/odoo-server/odoo/modules/loading.py", line 182, in load_module_graph
    _load_data(cr, module_name, idref, mode, kind='data')
  File "/odoo/odoo-server/odoo/modules/loading.py", line 96, in _load_data
    tools.convert_file(cr, module_name, filename, idref, mode, noupdate, kind, report)
  File "/odoo/odoo-server/odoo/tools/convert.py", line 846, in convert_file
    convert_xml_import(cr, module, fp, idref, mode, noupdate, report)
  File "/odoo/odoo-server/odoo/tools/convert.py", line 916, in convert_xml_import
    obj.parse(doc.getroot(), mode=mode)
  File "/odoo/odoo-server/odoo/tools/convert.py", line 797, in parse
    self.parse(rec, mode)
  File "/odoo/odoo-server/odoo/tools/convert.py", line 800, in parse
    self._tags[rec.tag](rec, de, mode=mode)
  File "/odoo/odoo-server/odoo/tools/convert.py", line 708, in _tag_record
    id = self.env(context=rec_context)['ir.model.data']._update(rec_model, self.module, res, rec_id or False, not self.isnoupdate(data_node), noupdate=self.isnoupdate(data_node), mode=self.mode)
  File "/odoo/odoo-server/odoo/addons/base/ir/ir_model.py", line 1252, in _update
    record = record.create(values)
  File "/odoo/odoo-server/odoo/addons/base/ir/ir_ui_view.py", line 365, in create
    return super(View, self).create(self._compute_defaults(values))
  File "/odoo/odoo-server/odoo/models.py", line 3887, in create
    self._fields[key].determine_inverse(record)
  File "/odoo/odoo-server/odoo/fields.py", line 1064, in determine_inverse
    getattr(records, self.inverse)()
  File "/odoo/odoo-server/odoo/addons/base/ir/ir_ui_view.py", line 220, in _inverse_arch
    view.write(data)
  File "/odoo/odoo-server/odoo/addons/base/ir/ir_ui_view.py", line 383, in write
    return super(View, self).write(self._compute_defaults(vals))
  File "/odoo/odoo-server/odoo/models.py", line 3595, in write
    self._write(old_vals)
  File "/odoo/odoo-server/odoo/models.py", line 3764, in _write
    self._validate_fields(vals)
  File "/odoo/odoo-server/odoo/models.py", line 1086, in _validate_fields
    raise ValidationError("%s\n\n%s" % (_("Error while validating constraint"), tools.ustr(e)))
ParseError: "Error while validating constraint

Field `subtotal_session` does not exist

Error context:
View `pos.session.form`
[view_id: 2257, xml_id: n/a, model: pos.session, parent_id: 1958]
None" while parsing /odoo/odoo-server/addons/pos_extend/views/pos_session.xml:4, near
<record id="view_pos_session_form_inherit" model="ir.ui.view">
			<field name="name">pos.session.form</field>
			<field name="model">pos.session</field>
			<field name="inherit_id" ref="point_of_sale.view_pos_session_form"/>
			<field name="arch" type="xml">
				<xpath expr="//separator" position="before">
							<field name="untaxamount_total" invisible="1"/>
							<field name="tax_amount" invisible="1"/>
							<field name="subtotal_session" invisible="1"/>
							<field name="number_of_order" invisible="1"/>
							<field name="total_discount" invisible="1"/>
							<field name="sale_qty" invisible="1"/>
							<field name="total_cancel_order" invisible="1"/>
							<field name="total_done_order" invisible="1"/>
				</xpath>
			</field>
		</record>

I installed and it gave errors

I install the app, no problem in setup, but with no result.