Make pipeline more resilliant to broken timestamps

[DanNixon]

Currently inability to decode a GPS timestamp is a panic.

On one hand this is sensible given that there is nothing at all that can be done with this data, the issue is that this makes a best effort recovery from this issue difficult.

In general the ability of the pipeline to cope with bad data in the frame metadata should be improved, but specifically the timestmaps given they are a key piece of data that must be formatted correctly.