Version 0.47.2

Fixed a file whose storage period is not known showing an end date anyway — one from years ago.

A file uploaded with credits while the browser could not read the storage network's clock records its end as epoch 0, and epoch 0 is the network's genesis. The row already said 「period unknown」 for that case — that half was fixed on 9 August — but the line under it still worked out a date from epoch 0 and printed it as the estimated end, which on the main network lands years in the past, and three screens each did that arithmetic themselves without checking for zero. There is now one place that answers the question, and it declines when the period is not known: no epoch, an epoch of zero or less, or no clock. When the period IS known, the same date appears exactly as before.