Description of problem:
# ipa privilege-add "Add User"
Description: Add user
--------------------------
Added privilege "Add User"
--------------------------
  Privilege name: Add User
  Description: Add user

# ipa privilege-add-permission --permissions="add hbac rule, delete hbac rule,
modify hbac rule" "Add User"
  Privilege name: Add User
  Description: Add user
  Permissions: Add HBAC rule, Delete HBAC rule, Modify HBAC rule
-----------------------------
Number of permissions added 3
-----------------------------


# ipa privilege-remove-permission --permissions="" "Add User"
ipa: ERROR: an internal error has occurred


Version-Release number of selected component (if applicable):
ipa-server-2.2.0-11.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1. Follow steps above


Actual results:
ipa: ERROR: an internal error has occurred

Expected results:
better error

Additional info:
[Thu Apr 26 10:14:43 2012] [error] ipa: INFO: admin@TESTRELM.COM:
privilege_remove_permission(u'Add User', all=False, raw=False, version=u'2.34',
permission=None): TypeError
[Thu Apr 26 10:15:24 2012] [error] ipa: INFO: admin@TESTRELM.COM:
privilege_add_permission(u'Add User', all=False, raw=False, version=u'2.34',
permission=(u'add hbac rule', u'delete hbac rule', u'modify hbac rule')):
SUCCESS
[Thu Apr 26 10:15:29 2012] [error] ipa: ERROR: non-public: TypeError:
'NoneType' object is not iterable
[Thu Apr 26 10:15:29 2012] [error] Traceback (most recent call last):
[Thu Apr 26 10:15:29 2012] [error]   File
"/usr/lib/python2.6/site-packages/ipaserver/rpcserver.py", line 320, in
wsgi_execute
[Thu Apr 26 10:15:29 2012] [error]     result = self.Command[name](*args,
**options)
[Thu Apr 26 10:15:29 2012] [error]   File
"/usr/lib/python2.6/site-packages/ipalib/frontend.py", line 438, in __call__
[Thu Apr 26 10:15:29 2012] [error]     ret = self.run(*args, **options)
[Thu Apr 26 10:15:29 2012] [error]   File
"/usr/lib/python2.6/site-packages/ipalib/frontend.py", line 716, in run
[Thu Apr 26 10:15:29 2012] [error]     return self.execute(*args, **options)
[Thu Apr 26 10:15:29 2012] [error]   File
"/usr/lib/python2.6/site-packages/ipalib/plugins/baseldap.py", line 2142, in
execute
[Thu Apr 26 10:15:29 2012] [error]     for attr in
options.get(self.reverse_attr, []):
[Thu Apr 26 10:15:29 2012] [error] TypeError: 'NoneType' object is not iterable
[Thu Apr 26 10:15:29 2012] [error] ipa: INFO: admin@TESTRELM.COM:
privilege_remove_permission(u'Add User', all=False, raw=False, version=u'2.34',
permission=None): TypeError