It is difficult to decide whether we are dealing here with one authentic version or with two authentic ones. FE1 has no accidentals in this bar, and such sloppy notation (naturals are obviously needed to lower d
to d) suggests that also the 
lowering G to G could have been omitted. On the other hand, it i s precisely this observation that could have inspired the reviser of GE to add a in that place, so both G and G could possibly be the only authentic version. For that reason we decide to have a variant solution.
In versions with the natural we add a cautionary 
before g in the following bar.
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources; Editorial revisions
issues: Omission of current key accidentals
notation: Pitch