Description of problem:
After updating virt-manager to 0.10.0-3 yesterday, I can no longer create new domains. I further updated to 0.10.0-4 today, but the problem remains.

Version-Release number of selected component (if applicable):
virt-manager-0.10.0-3.fc19.noarch
virt-manager-common-0.10.0-3.fc19.noarch
virt-install-0.10.0-3.fc19.noarch

and 
virt-manager-0.10.0-4.fc19.noarch
virt-manager-common-0.10.0-4.fc19.noarch
virt-install-0.10.0-4.fc19.noarch


How reproducible:
always

Steps to Reproduce:
1. start vitr-manager
2. us the wizard to create a new domain
3. It does not really matter what you select, after step 5/5 the wizard will show an error message:

Actual results:

Nicht erfasster Fehler bei Validierung von Installationsparametern: 'NoneType' object has no attribute 'set_parent'

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/create.py", line 1481, in validate
    return self.validate_storage_page(oldguest=oldguest)
  File "/usr/share/virt-manager/virtManager/create.py", line 1744, in validate_storage_page
    self.conn, disk.path)
  File "/usr/share/virt-manager/virtManager/uihelpers.py", line 938, in check_path_search_for_qemu
    set_error_parent(parent)
  File "/usr/share/virt-manager/virtManager/uihelpers.py", line 52, in set_error_parent
    err_dial.set_parent(parent)
AttributeError: 'NoneType' object has no attribute 'set_parent'


"Nicht erfasster Fehler..." means something like "uncaught error while validating install parameters".

Expected results:
should work as it did with before

Additional info:
File -> Exit does not work either, I have to quit virt-manager by clisin