The ornamental design of a sporttrailer with side panels, as shown and described.
FIG. 1 is a front perspective view of the sport trailer;
FIG. 2 is a back perspective view of the sport trailer;
FIG. 3 is a front elevation view of the sport trailer;
FIG. 4 is a back elevation view of the sport trailer;
FIG. 5 is a right side elevation view of the sport trailer;
FIG. 6 is a left side elevation view of the sport trailer;
FIG. 7 is a top plan view of the sport trailer; and,
FIG. 8 is a bottom plan view of the sport trailer.
The broken lines in FIGS. 1-8 setting forth additional portions of the sport trailer are for illustrative purposes only and form no part of the claimed design.