The ornamental design for a rivetgunsafetyguard, as shown and described.
FIG. 1 is a front perspective view of a rivet gun safety guard showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof; and,
FIG. 5 is a right side elevation view thereof, to which the top plan and bottom plan views are identical and the opposing left side elevation view is a mirror image.