Error in muon analysis window

[jclarkeSTFC]

Found in manual testing for the 6.10 release, this is a regression from 6.9.

Follow the Transverse Field Asymmetry Test instructions of the MUSR page. For the Simultaneous over section, when changing the Fitting type from Normal to TF Asymmetry and attempting fit, I get the following error:

Traceback (most recent call last):
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\fitting_widgets\tf_asymmetry_fitting\tf_asymmetry_fitting_presenter.py", line 80, in handle_tf_asymmetry_mode_changed
    self.fitting_mode_changed_notifier.notify_subscribers()
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqt\utils\observer_pattern.py", line 101, in notify_subscribers
    Observable.notify_subscribers(self, *args)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqt\utils\observer_pattern.py", line 56, in notify_subscribers
    self.thread_safe_update_call(arg, **kwargs)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqt\utils\qt\qappthreadcall.py", line 69, in __call__
    return self._callable(*args)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqt\utils\observer_pattern.py", line 60, in _notify_subscribers_impl
    observer.update(self, arg, **kwargs)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqt\utils\observer_pattern.py", line 84, in update
    self.callback()
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\seq_fitting_tab_widget\seq_fitting_tab_presenter.py", line 81, in handle_selected_workspaces_changed
    self.handle_fit_function_updated()
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\seq_fitting_tab_widget\seq_fitting_tab_presenter.py", line 54, in handle_fit_function_updated
    parameter_values = self._get_fit_function_parameter_values_from_fitting_model()
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\seq_fitting_tab_widget\seq_fitting_tab_presenter.py", line 60, in _get_fit_function_parameter_values_from_fitting_model
    parameter_values = [
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\seq_fitting_tab_widget\seq_fitting_tab_presenter.py", line 61, in <listcomp>
    self.model.get_all_fit_function_parameter_values_for(fit_function)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\fitting_widgets\tf_asymmetry_fitting\tf_asymmetry_fitting_model.py", line 703, in get_all_fit_function_parameter_values_for
    return self._get_all_fit_function_parameter_values_for_tf_simultaneous_function(fit_function)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\fitting_widgets\tf_asymmetry_fitting\tf_asymmetry_fitting_model.py", line 722, in _get_all_fit_function_parameter_values_for_tf_simultaneous_function
    normal_domain_function = self._get_normal_fit_function_from(tf_domain_function)
  File "C:\MantidNightlyInstall\bin\lib\site-packages\mantidqtinterfaces\Muon\GUI\Common\fitting_widgets\tf_asymmetry_fitting\tf_asymmetry_fitting_model.py", line 306, in _get_normal_fit_function_from
    return tf_asymmetry_function.getFunction(0).getFunction(1).getFunction(1)
RuntimeError: Function ExpDecayMuon doesn't have children.

Platform/Version (please complete the following information):

• OS: Windows
• OS Version: 10
• Mantid Version v6.9.20240514.1920

[github-actions]

Closed by #37395.