The ornamental design for a handbag, as shown and described.
FIG. 1 is a perspective view of a handbag showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines surrounding portions without surface shading depict portions of the article and form no part of the claim. The broken lines crossing claimed surfaces depict stitching and form no part of the claim.