The ornamental design for a handbag, as shown and described.
FIG. 1 is a front elevational view of the handbag showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a right side elevational view thereof, the left side elevational view being a mirror image thereof;
FIG. 4 is a rear elevational view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken lines in FIGS. 1-5 show the stitching and are part of the claimed design, and the broken lines in FIGS. 1, 3, 4 and 5 showing supporting legs at the bottom of the handbag are for the purposes of illustrating environment and form no part of the claimed design.