The ornamental design for a topless buckethat, as shown and described.
FIG. 1 is a perspective view of a topless bucket hat, showing my new design;
FIG. 2 is a front elevation view thereof, the rear elevation view being a mirror image thereof;
FIG. 3 is a left-side elevation view thereof;
FIG. 4 is a right-side elevation view thereof; and,
FIG. 5 is a top plan view thereof.
The even-sized dash-dash broken lines shown in the drawings depict portions of the topless bucket hat that form no part of the claimed design, while the uneven-sized dot-dash broken lines depict the bounds of the claimed design, it being understood that the claimed design extends to this boundary but does not include the boundary.