I claim the ornamental design for a bracket for a rack, as shown and described.
FIG. 1 is a perspective view of a bracket for a rack, showing the front, top and right side of a rear part of one bracket, according to an embodiment of the invention;
FIG. 2 is a top plan view of the bracket for a rack according to FIG. 1;
FIG. 3 is a bottom plan view of the bracket for a rack according to FIG. 1;
FIG. 4 is a rear view of the bracket for a rack according to FIG. 1;
FIG. 5 is a right side view of the bracket for a rack according to FIG. 1; and,
FIG. 6 is a left side view of the bracket for a rack according to FIG. 1.
The broken lines in the drawings illustrate portions of the bracket for a rack which form no part of the claimed design. The non-oblique line shading is meant to show contour of represented surfaces, not surface ornamentation.