The ornamental design for a handbag, as shown and described.
FIG. 1 is a front elevational view of a handbag;
FIG. 2 is a rear ¾ perspective view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is an open interior top view thereof.
The dotted lines on the surface of the claimed design represent unclaimed stitching. The criss-cross pattern applied to specific surface areas is intended to represent different fabric material from the rest of the handbag. The broken lines shown in the figures are included for the purpose of illustrating the environment in which the design is used and form no part of the claimed design.