The ornamental design for a light stringholder, as shown and described.
FIG. 1 is a front perspective view of the light string holder according to
my design;
FIG. 2 is a front elevational view of the light string holder according to
FIG. 1;
FIG. 3 is a side elevational view of the light string holder according to
FIG. 1, the remaining two sides of the light string holder according to
FIG. 1 being identical in ornamentation to that shown in this FIG.;
FIG. 4 is a bottom plan view of the light string holder according to FIG.
1; and,
FIG. 5 is an top view of the light string holder according to FIG. 1.