In GE1 (→GE2), all grace notes are non-slashed in these bars, which is one of the indications of evident distraction of the engraver of GE1 in bars 299-302 (other mistakes include an overlooked quaver flag in bar 300, an erroneous last semiquaver in the L.H. in bar 300, Terzverschreibung errors in the chords in bars 300 and 302 as well as, most probably, three overlooked 
marks in bars 299-301). The grace notes were written correctly in GE3.
Compare the passage in the sources »
category imprint: Differences between sources
issues: Inaccuracies in GE, GE revisions
notation: Ornaments