"An unknown error has occurred" is output when installing RHEL8 via anaconda

Issue

• The error below is output when installing RHEL8 via anaconda to the host.

An unknown error has occurred
This program has encountered an unknown error. You may report the bug below or quit the program

• The following errors can be found in the anaconda.log

Traceback (most recent call first):
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/spokes/lib/resize.py", line 292, in _update_action_buttons
    self._shrinkButton.set_sensitive(obj.editable and not device.is_disk)
  File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/gui/spokes/lib/resize.py", line 494, in on_selection_changed
    self._update_action_buttons(self._diskStore[itr])
AttributeError: 'NoneType' object has no attribute 'is_disk'