The ornamental design for a portableashtray, as shown and described.
FIG. 1 is a front perspective view of a portable ashtray in an open condition;
FIG. 2 is a front perspective view of the portable ashtray in a closed condition;
FIG. 3 is a front view of the portable ashtray;
FIG. 4 is a right side view of the portable ashtray;
FIG. 5 is a left side view of the portable ashtray;
FIG. 6 is a top view of the portable ashtray;
FIG. 7 is a bottom view of the portable ashtray; and,
FIG. 8 is a front perspective view of the portable ashtray in use.
The broken lines in FIG. 7 depict a portion of the portable ashtray that forms no part of the claimed design. The broken lines in FIG. 8 depict environment that forms no part of the claimed design.