Better reporting of missing LC calculation values

https://github.com/rzellem/EXOTIC/blob/main/exotic/exotic.py#L1717

When EXOTIC cannot create the lightcurve because one of the core values required for the calculations is missing, e.g. flux, timing or airmass, are either empty or infinite values it is simply printing, "No data left after filtering." 

It would help to tell the user which data is actually missing: flux, timing or airmass.