Changed the way variables fetch parameters through getters. They now return NaN instead of raising KeyError. This allows for more complex queries like superEarths = [planet for planet in oecDB.planets if planet.R < (10 * oec.R_e)]

Before the above query would return KeyError if any planet had a missing M value. Now it will return np.NaN. NaN was used as unlike False and None, NaN < 1 and NaN > 1 are both False