The version of FE (a chord with f) is a result of Chopin proofreading from the version of the remaining sources (a chord with a). The traces of performing changes in print are present in FE both in this bar and in analogous bar 105. In a similar place in bar 36, all sources feature a chord with f.
Compare the passage in the sources »
category imprint: Differences between sources; Corrections & alterations
issues: Accompaniment changes, Authentic corrections of FE
notation: Pitch