The ornamental design for a portableheater, as shown and described.
FIG. 1 is an isometric view of a portable heater in a first operating position showing our new design;
FIG. 2 is a first side view of the portable heater of FIG. 1 in the first operating position, with the second side view of the portable heater in the first operating position being a mirror image of the first side view;
FIG. 3 is a front view of the portable heater of FIG. 1 in the first operating position;
FIG. 4 is a rear view of the portable heater of FIG. 1 in the first operating position;
FIG. 5 is a top view of the portable heater of FIG. 1 in the first operating position;
FIG. 6 is a bottom view of the portable heater of FIG. 1 in the first operating position;
FIG. 7 is an isometric view of the portable heater of FIG. 1 in a second operating position; and,
FIG. 8 is a first side view of the portable heater of FIG. 1 in the second operating position, with the second side view of the portable heater in the second operating position being a mirror image of the first side view.
The broken lines in the Figures depict portions of the portable heater that form no part of the claimed design.