CLAIMThe ornamental design for a stapler, as shown and described.
FIG. 1 is a top perspective view of a stapler;
FIG. 2 is a left side view of the stapler;
FIG. 3 is a right side view of the stapler;
FIG. 4 is a front view of the stapler;
FIG. 5 is a rear view of the stapler;
FIG. 6 is a top plan view of the stapler;
FIG. 7 is a bottom plan view of the stapler; and,
FIG. 8 is a bottom perspective view of the stapler.