Repoint - Check the behavior of repoint data with NaNs

[subagonsouth]

Algorithm Description:

Under certain conditions, we may get a repoint table that has a valid start time for a repoint with NaNs for the end times. This ticket is to double check that the spice.repoint module handles these tables correctly (whatever correctly means).

This may be a non-issue because normally, we wont kick off processing for a Pointing until the pointing is complete meaning that the NaNs should have been filled and the next repoint start time reported. But, it might be possible due to a data gap that we get the next repoint start time without filling the previous repoint end time NaN values.