I see the error is in:

File "/home/odoo/src/odoo/16.0/addons/account/models/account_journal_dashboard.py", line 162, in get_line_graph_datas
    amount = currency.round(amount - val['amount'])
TypeError: unsupported operand type(s) for -: 'int' and 'NoneType'

One of the values are not defined.

Traceback (most recent call last):
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 983, in get
    cache_value = field_cache[record._ids[0]]
KeyError: 17

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1139, in __get__
    value = env.cache.get(record, self)
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 990, in get
    raise CacheMiss(record, field)
odoo.exceptions.CacheMiss: 'account.journal(17,).kanban_dashboard'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 983, in get
    cache_value = field_cache[record._ids[0]]
KeyError: 17

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1139, in __get__
    value = env.cache.get(record, self)
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 990, in get
    raise CacheMiss(record, field)
odoo.exceptions.CacheMiss: 'account.journal(17,).kanban_dashboard_graph'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/16.0/odoo/http.py", line 1579, in _serve_db
    return service_model.retrying(self._serve_ir_http, self.env)
  File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 134, in retrying
    result = func()
  File "/home/odoo/src/odoo/16.0/odoo/http.py", line 1608, in _serve_ir_http
    response = self.dispatcher.dispatch(rule.endpoint, args)
  File "/home/odoo/src/odoo/16.0/odoo/http.py", line 1805, in dispatch
    result = self.request.registry['ir.http']._dispatch(endpoint)
  File "/home/odoo/src/odoo/16.0/addons/website/models/ir_http.py", line 235, in _dispatch
    response = super()._dispatch(endpoint)
  File "/home/odoo/src/odoo/16.0/odoo/addons/base/models/ir_http.py", line 144, in _dispatch
    result = endpoint(**request.params)
  File "/home/odoo/src/odoo/16.0/odoo/http.py", line 698, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo/src/odoo/16.0/addons/web/controllers/dataset.py", line 42, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/odoo/src/odoo/16.0/addons/web/controllers/dataset.py", line 33, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 457, in call_kw
    result = _call_kw_model(method, model, args, kwargs)
  File "/home/odoo/src/odoo/16.0/odoo/api.py", line 430, in _call_kw_model
    result = method(recs, *args, **kwargs)
  File "/home/odoo/src/odoo/16.0/addons/web/models/models.py", line 62, in web_search_read
    records = self.search_read(domain, fields, offset=offset, limit=limit, order=order)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 4968, in search_read
    result = records.read(fields, **read_kwargs)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 2994, in read
    return self._read_format(fnames=fields, load=load)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 3132, in _read_format
    vals[name] = convert(record[name], record, use_name_get)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 5851, in __getitem__
    return self._fields[key].__get__(self, type(self))
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1188, in __get__
    self.compute_value(recs)
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1347, in compute_value
    records._compute_field_value(self)
  File "/home/odoo/src/odoo/16.0/addons/mail/models/mail_thread.py", line 403, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 4196, in _compute_field_value
    getattr(self, field.compute)()
  File "/home/odoo/src/odoo/16.0/addons/account/models/account_journal_dashboard.py", line 21, in _kanban_dashboard
    journal.kanban_dashboard = json.dumps(journal.get_journal_dashboard_datas())
  File "/home/odoo/src/odoo/16.0/addons/account_check_printing/models/account_journal.py", line 85, in get_journal_dashboard_datas
    super(AccountJournal, self).get_journal_dashboard_datas(),
  File "/home/odoo/src/odoo/16.0/addons/account/models/account_journal_dashboard.py", line 329, in get_journal_dashboard_datas
    is_sample_data = self.kanban_dashboard_graph and any(data.get('is_sample_data', False) for data in json.loads(self.kanban_dashboard_graph))
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1188, in __get__
    self.compute_value(recs)
  File "/home/odoo/src/odoo/16.0/odoo/fields.py", line 1347, in compute_value
    records._compute_field_value(self)
  File "/home/odoo/src/odoo/16.0/addons/mail/models/mail_thread.py", line 403, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/16.0/odoo/models.py", line 4196, in _compute_field_value
    getattr(self, field.compute)()
  File "/home/odoo/src/odoo/16.0/addons/account/models/account_journal_dashboard.py", line 28, in _kanban_dashboard_graph
    journal.kanban_dashboard_graph = json.dumps(journal.get_line_graph_datas())
  File "/home/odoo/src/odoo/16.0/addons/account/models/account_journal_dashboard.py", line 162, in get_line_graph_datas
    amount = currency.round(amount - val['amount'])
TypeError: unsupported operand type(s) for -: 'int' and 'NoneType'

The above server error caused the following client error:
OwlError: An error occured in the owl lifecycle (see this Error's "cause" property)
    at handleError (https://smf-inso-database.odoo.com/web/assets/514-1fa4aba/web.assets_common.min.js:1212:101)
    at owl.App.handleError (https://smf-inso-database.odoo.com/web/assets/514-1fa4aba/web.assets_common.min.js:2040:29)
    at ComponentNode.initiateRender (https://smf-inso-database.odoo.com/web/assets/514-1fa4aba/web.assets_common.min.js:1518:19)

Caused by: RPC_ERROR: Odoo Server Error
    at makeErrorFromResponse (https://smf-inso-database.odoo.com/web/assets/519-9c1c7d9/web.assets_backend.min.js:975:163)
    at XMLHttpRequest. (https://smf-inso-database.odoo.com/web/assets/519-9c1c7d9/web.assets_backend.min.js:982:13)