title: Issue generating payslip in odoo 13
body: <p>For some reason I am getting error when I am trying to confirm the payslip for two particular users. The error I am getting is as follows</p>
  <pre><code>Error:
  Odoo Server Error
  
  Traceback (most recent call last):
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 624, in _handle_exception
      return super(JsonRequest, self)._handle_exception(exception)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 310, in _handle_exception
      raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/tools/pycompat.py&quot;, line 14, in reraise
      raise value
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 669, in dispatch
      result = self._call_function(**self.params)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 350, in _call_function
      return checked_call(self.db, *args, **kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/service/model.py&quot;, line 94, in wrapper
      return f(dbname, *args, **kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 339, in checked_call
      result = self.endpoint(*a, **kw)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 915, in __call__
      return self.method(*args, **kw)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/http.py&quot;, line 515, in response_wrap
      response = f(*args, **kw)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/addons/web/controllers/main.py&quot;, line 1331, in call_button
      action = self._call_kw(model, method, args, kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/addons/web/controllers/main.py&quot;, line 1319, in _call_kw
      return call_kw(request.env[model], method, args, kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/api.py&quot;, line 387, in call_kw
      result = _call_kw_multi(method, model, args, kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/api.py&quot;, line 374, in _call_kw_multi
      result = method(recs, *args, **kwargs)
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/addons/dt_payroll_multi_currency/models/hr_payslip.py&quot;, line 53, in action_multi_currency
      'debit': val.amount * self._get_conversion_rate(from_currency, to_currency, company, date),
    File &quot;/opt/bitnami/apps/odoo/lib/odoo-13.0.post20210215-py3.7.egg/odoo/addons/dt_payroll_multi_currency/models/hr_payslip.py&quot;, line 20, in _get_conversion_rate
      res = currency_rates.get(to_currency.id) / currency_rates.get(from_currency.id)
  TypeError: unsupported operand type(s) for /: 'float' and 'NoneType'
  </code></pre>
  <p>I have not made any change to the source files, and the payslips are generated fine for these users on different months. Any reason as to why this might be happening? Any particular documentation that might be helpful?</p>