Erratum:'A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo'

This erratum reports two errors, found respectively in the gwcosmo codebase used for estimating the Hubble constant H₀ (Gray et al. 2020), and an associated galaxy catalog preprocessing script, both of which affect the results of the published article (Abbott et al. 2021).