The ornamental design of a handbag, as shown and described.
FIG. 1 is a perspective view of a handbag;
FIG. 2 is a bottom plan view of a handbag;
FIG. 3 is a top plan view of a handbag;
FIG. 4 is a front elevational view of a handbag;
FIG. 5 is a rear elevational view of a handbag;
FIG. 6 is a left-side elevational view of a handbag; and,
FIG. 7 is a right-side elevational view of a handbag.
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.