[PATCH] fix traceback on 'autoqa post-koji-build -l'

[Kamil Paral]

I don't know if this patch is the best solution, I would have to study the
code longer, but it certainly fixes the traceback:

Traceback (most recent call last):
  File "/usr/bin/autoqa", line 166, in <module>
    testlist = hook.process_testlist(opts, args, testlist)
  File "/usr/share/autoqa/post-koji-build/hook.py", line 31, in process_testlist
    if 'x86_64' not in opts.arch and 'rpmlint' in testlist:
TypeError: argument of type 'NoneType' is not iterable