Oliver Woodman fae6c65367 Be robust against manifests that don't define top level duration explicitly.
I think such manifests are invalid, and I haven't seen any examples,
but given it's trivial to fill in the duration if the periods define
durations, it seems worth being robust.
2015-09-01 14:19:06 +01:00
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2015-08-04 16:07:54 +01:00