The ornamental design for a door of a compactor, as shown and described.
FIG. 1 is a front, top, left perspective view of a door of a compactor showing the new design;
FIG. 2 is rear, top, right perspective view thereof;
FIG. 3 is front elevation view thereof;
FIG. 4 is rear elevation view thereof;
FIG. 5 is left side elevation view thereof;
FIG. 6 is right side view thereof;
FIG. 7 is top plan view thereof; and,
FIG. 8 is bottom plan view thereof.
The claimed design includes the mirror image of the designs depicted in FIGS. 1 to 8. The broken lines of even length shown in the drawings illustrate portions of the door of the compactor that form no part of the claimed design.