FIG. 1 is a front view of a heater showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a perspective view thereof.

The broken line showing of the two slant holes at the bottom and the two circular holes at the top as illustrated in FIGS. 2, 3 and 4 is for the purpose of illustrating environmental structure and forms no part of the claimed design.