The ornamental design for a handbag, as shown and described.
FIG. 1 is a front perspective view of a handbag showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof, with the shoulder strap shown in an alternate position.
The broken lines that depict the inner edge of the closure flap in FIGS. 1, 4, 5, and 7 are for the purpose of showing portions of the article that form no part of the claim.