I claim the ornamental design for a hammock liner, as shown and described.
FIG. 1 is a perspective view of a hammock liner, showing my new design;
FIG. 2 is a top plan view of the invention;
FIG. 3 is a bottom plan view of the invention;
FIG. 4 is a left-side elevational view of the invention, the right-side elevational view being a mirror image thereof; and,
FIG. 5 is a front elevational view of the invention, the rear elevational view being a mirror image thereof.
The broken lines showing a hammock in FIG. 1 are included for the purpose of illustrating the invention in use, and form no part of the claimed design.