BUGZILLA-1111383 Don't assume that 'kind' is a valid key

'kind' is not necessarily emitted during a declDef record creation,
so we should provide a default value of None to avoid crashing.

https://bugzilla.mozilla.org/show_bug.cgi?id=1111383
I don't believe this one is necessary; all the CSV lines that begin with "type" (i.e., the ones yielded by `silent_itemgetter('type')` in indexers.py) always have a `kind` field, and `kind_getter('ref', 'type')`, with your change above, will no longer return kindless records. Please correct me if I missed something.