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; and,
FIG. 6 is a top view of the handbag shown in FIG. 1.
The broken lines immediately adjacent the shaded areas represent the bounds of the claim and all other broken lines are for illustrative purposes only. None of the broken lines form a part of the claimed design.