This is the second of the places in which Chopin changed the melodic line of the Etude (cf. bar 28). The final version is present in Ap, it was also already written in the base text for FE.
In one of the last proofreadings of FE (→EE) a cautionary was added before the 14th semiquaver a1. In this context the sign seems to be totally unnecessary.
Compare the passage in the sources »
category imprint: Differences between sources
issues: Cautionary accidentals, Authentic corrections of FE, Main-line changes
notation: Pitch