It's actually a good question. The two best editions (Wiener Urtext, and Paderewski) both have that measure written as dotted rhythm in the lh. Chopin was using a notational convention that was still employed in his day -where you have triplets in one hand against two notes in the other, the hand with two notes would be written as dotted rhythm. This goes back to Bach. In practice, you play the left hand as eighths and sixteenths, and they correspond with the rh (or as the first example shows).