The ornamental design for a dispenser for wastebags.
FIG. 1 is a front elevational view of a dispenser for waste bags showing our new design;
FIG. 2 is a right side elevational view thereof
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a perspective view thereof.
The broken-line disclosure is understood to represent portions of the article in which the claimed design is embodied, but which form no part of the claimed design.