The ornamental design for a handbag, as shown and described.
FIG. 1 is a rear left perspective view of a handbag showing my new design, where the shoulder strap is draped around the rear face to connecting points on the left and right sides of the handbag;
FIG. 2 is a rear elevation view of the handbag in an alternate configuration, where the shoulder strap is draped around the front face to connecting points on the left and right sides of the handbag;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view of the configuration shown in FIG. 1;
FIG. 6 is a bottom view of the configuration shown in FIG. 2; and,