The ornamental design for a handbag, as shown and described.
FIG. 1 is a back view of a handbag according to my new design;
FIG. 2 is a front view of the handbag shown in FIG. 1;
FIG. 3 is a left side view of the handbag shown in FIG. 1;
FIG. 4 is a right side view of the handbag shown in FIG. 1;
FIG. 5 is a top view of the handbag shown in FIG. 1;
FIG. 6 is a bottom view of the handbag shown in FIG. 1; and,
FIG. 7 is a top frontal perspective view of the handbag shown in FIG. 1.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines shown in the drawings represent stitching, which is part of the claimed design.