The ornamental design for an rvhitchballcover, as shown and described.
FIG. 1 is a top, rear, left side perspective view of an RV hitch ball cover showing our new design;
FIG. 2 is a bottom, front, right side perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a rear elevational view thereof;
FIG. 8 is a front elevational view thereof; and,
FIG. 9 is a right side elevational view of an alternate embodiment having broken lines which illustrate portions of the hitch ball cover that form no part of the claim.