The ornamental design for a handbag, as shown and described.
FIG. 1 is a front isometric view of the handbag of the present invention;
FIG. 2 is second isometric view thereof;
FIG. 3 is bottom isometric view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a right-side view thereof;
FIG. 7 is a left-side view thereof;
FIG. 8 is a top plan view thereof; and,
FIG. 9 is a bottom plan view thereof.
The broken lines shown represent stitching and form part of the claimed design. The dot-dashed broken lines represent boundaries to disclaim the interior of the handbag.