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 of the handbag shown in FIG. 1;
FIG. 3 is a rear view of the handbag shown in FIG. 1;
FIG. 4 is a left side view of the handbag shown in FIG. 1;
FIG. 5 is a right side view of the handbag shown in FIG. 1;
FIG. 6 is a top view of the handbag shown in FIG. 1; and,
FIG. 7 is a bottom view of the handbag shown in FIG. 1.
The broken line showing of the handles, rivets, zipper, zipper pull, rectangular plaque, and rear and side portions of the body of the bag is for illustrative purposes only and forms no part of the claimed design.