I claim the ornamental design for an ergonomic tray, as shown and described.
FIG. 1 is an isometric view of the ergonomic tray showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a front view thereof;
FIG. 8 is a front view shown in environment thereof; and,
FIG. 9 is a rear view shown in environment thereof.
The broken lines showing a person and a chair in FIG. 8 and FIG. 9 are included for the purposes of illustrating environment and form no part of the claimed design.