The ornamental design for a handbag, as shown and described.
FIG. 1 is a front perspective view of the handbag showing our design;
FIG. 2 is a is a front elevational view of the handbag;
FIG. 3 is a rear elevational view of the handbag;
FIG. 4 is an elevational view of the left side of the handbag;
FIG. 5 is an elevational view of the right side of the handbag;
FIG. 6 is a top view of the handbag; and,
FIG. 7 is a bottom view of the handbag.
The dash lines show stitching which is part of our design with the exception of the teardrop shaped elements on FIG. 7, the bottom view of the handbag, which teardrop shaped broken lines are for illustrative purposes only and form no part of the claimed design.