The ornamental design for a tubfiller, as shown and described.
FIG. 1 is a front perspective view of a tub filler showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line adjacent the image near the midpoint of the neck forms an unclaimed boundary of the design. The broken line showing of the remainder of the tub filler is for environmental purposes only and forms no part of the claimed design.