In EE, GC and FE1 there is no 
augmenting a2 to
a
2. This obvious inaccuracy must have been already present in the autograph (such inaccurate notation is quite common in Chopin's autographs). The accidental was added in GE and FE2, which must have been done by the revisors. Compare b. 345.
Compare the passage in the sources »
category imprint: Differences between sources
issues: Accidentals in different octaves, Inaccuracies in FE, GE revisions, EE inaccuracies, FE revisions, Inaccuracies in GC
notation: Pitch