digital_ocean #3438: use get instead of [] to prevent KeyError

This works on my system and seems correct by inspection.   The reporter has not confirmed if this fixes his problem, but this code is less error-prone.

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The existing code was using:
  a[b][c[d]]
where a[b] would always exist and c[d] would always exist.
But the nested index would not alway exist, particularly when a DigitalOcean item disapeared.

This changes that nested index to a `get` and properly handles None results.

This bug was present in two spots in this file.