The ornamental design for a handbag, as shown and described.
FIG. 1 is a top, front, right perspective view of a handbag showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a left elevation view thereof; and,
FIG. 7 is a right elevation view thereof.
In FIG. 5, all of the broken lines shown in the center of the bottom surface of the handbag illustrate portions of the article that form no part of the claimed design. The remaining dashed lines in all views represent stitching and form part of the claimed design.