Description of problem:
After recent updates in f33 i've got this error when trying to edit CPU section:

  Error refreshing hardware page: attrib must be dict, not NoneType


Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/details/details.py", line 1025, in hw_selected
    self.refresh_config_cpu()
  File "/usr/share/virt-manager/virtManager/details/details.py", line 2223, in refresh_config_cpu
    if not self._cpu_secure_is_available():
  File "/usr/share/virt-manager/virtManager/details/details.py", line 2167, in _cpu_secure_is_available
    features = domcaps.get_cpu_security_features()
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 308, in get_cpu_security_features
    cpu = self._get_expanded_cpu(m)
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 273, in _get_expanded_cpu
    cpuXML = self._convert_mode_to_cpu(mode.get_xml())
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 267, in _convert_mode_to_cpu
    root.attrib = None
TypeError: attrib must be dict, not NoneType



Version-Release number of selected component (if applicable):
virt-manager-2.2.1-3.fc32 (f32 package!)


How reproducible:
Open virt-manager and try edit CPU section new or old one existed VM.


Actual results:
  Error refreshing hardware page: attrib must be dict, not NoneType

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/details/details.py", line 1025, in hw_selected
    self.refresh_config_cpu()
  File "/usr/share/virt-manager/virtManager/details/details.py", line 2223, in refresh_config_cpu
    if not self._cpu_secure_is_available():
  File "/usr/share/virt-manager/virtManager/details/details.py", line 2167, in _cpu_secure_is_available
    features = domcaps.get_cpu_security_features()
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 308, in get_cpu_security_features
    cpu = self._get_expanded_cpu(m)
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 273, in _get_expanded_cpu
    cpuXML = self._convert_mode_to_cpu(mode.get_xml())
  File "/usr/share/virt-manager/virtinst/domcapabilities.py", line 267, in _convert_mode_to_cpu
    root.attrib = None
TypeError: attrib must be dict, not NoneType


Expected results:
No such error. And ability to apply changes as before