We claim the ornamental design for a handheld electronic device, as shown and described.
FIG. 1 is a front perspective view of a handheld electronic device;
FIG. 2 is a back perspective view of the handheld electronic device;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a back elevational view thereof;
FIG. 5 is a right elevational view thereof;
FIG. 6 is a left elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown throughout the views, which are immediately adjacent to the shaded areas and define unshaded regions, represent the bounds of the claimed design, while all other broken lines are directed to environment and are for illustrative purposes only; the broken lines form no part of the claimed design.