The ornamental design for a tablebase, as shown and described.
FIG. 1 is a top plan view of a table base showing my design;
FIG. 2 is a side elevational view;
FIG. 3 is an end elevational view; and
FIG. 4 is a perspective view of the table base on an enlarged scale.
The side and end not shown in FIGS. 2 and 3 are like the respective side
and end shown while the appearance of the base is a mirror image of the
top as shown in FIG. 1.