AttributeError: 'NoneType' object has no attribute 'verfers' for "sig-fix"

[daidoji]

Version

0.4.1

Environment

linux, 3.14

Expected behavior

sig-fix command should work for all wallets.

Actual behavior

While attempting to run sig-fix command on very old wallets we got the following stack trace.

Traceback (most recent call last):
File "/keria/.venv/bin/keria", line 10, in
sys.exit(main())
~~~~^^
File "/keria/.venv/lib/python3.13/site-packages/keria/app/cli/keria.py", line 27, in main
raise ex
File "/keria/.venv/lib/python3.13/site-packages/keria/app/cli/keria.py", line 22, in main
args.handler(args)
~~~~~~~~~~~~^^^^^^
File "/keria/.venv/lib/python3.13/site-packages/keria/app/cli/commands/sig-fix.py", line 25, in
parser.set_defaults(handler=lambda args: handler(args), transferable=True)
~~~~~~~^^^^^^
File "/keria/.venv/lib/python3.13/site-packages/keria/app/cli/commands/sig-fix.py", line 40, in handler
return directing.runController([doing.doify(fix, **kwa)], expire=0.0)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/keria/.venv/lib/python3.13/site-packages/keri/app/directing.py", line 678, in runController
doist.do(doers=doers)
~~~~~~~~^^^^^^^^^^^^^
File "/keria/.venv/lib/python3.13/site-packages/hio/base/doing.py", line 156, in do
self.recur() # increments .tyme runs recur context
~~~~~~~~~~^^
File "/keria/.venv/lib/python3.13/site-packages/hio/base/doing.py", line 275, in recur
tock = dog.send(self.tyme) # yielded tock == 0.0 means re-run asap
File "/keria/.venv/lib/python3.13/site-packages/keria/app/cli/commands/sig-fix.py", line 125, in fix
for v in hab.kever.verfers:
^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'verfers'

Steps to reproduce

Get a really old wallet (probably from before verfers existed) and try to run the sig-fix command against it.