Description of problem:
system-config-printer causes traceback on wrong configured printer.

Version-Release number of selected component (if applicable):
foomatic-3.0.2-3
system-config-printer-0.6.116.10-1
foomatic-3.0.2-3.1

How reproducible:
Always

Steps to Reproduce:
Use system-config-printer-0.6.116.10-1 and foomatic-3.0.2-3

1. Import the PPD from
http://www.linuxprinting.org/download/oldPPDs/HP/mono_laser/HP_LaserJet_8100_Series.ppd
2. Create a new printer using the imported PPD as driver
3. Select "Edit" from context menu in printer list

it will cause a traceback (as in bug #207965).

Then upgrade to foomatic-3.0.2-3.1. Start system-config-printer, hit "Edit"
button and it will cause a traceback too. 

When creating new printer from imported PPD (with new foomatic) and then hitting
"Edit" - no traceback occurs. 

Actual results:

Traceback -

Couldn't load driver information.Traceback (most recent call last):
  File "/usr/share/printconf/util/queueTree.py", line 599, in
edit_button_clicked
    if self.editQueue.editQueueDialog (iter):
  File "/usr/share/printconf/util/editQueue.py", line 414, in
editQueueDialog
    self.write_driver_options ()
  File "/usr/share/printconf/util/editQueue.py", line 919, in
write_driver_options
    for option_tuple in option_list:
TypeError: iteration over non-sequence

Expected results:
A window with editable options should pop up