I claim the ornamental design for a needle threader, as shown and described.
FIG. 1 is a front view of a needle threader showing my design, the rear view being a mirror image;
FIG. 2 is a left side view of the same needle threader;
FIG. 3 is a right side view of the same needle threader;
FIG. 4 is a top plan view of the same needle threader;
FIG. 5 is a bottom view of the same needle threader;
FIG. 6 is a front view similar to FIG. 1 but showing the same needle threader with the threading plate pivoted into the housing when the needle threader is out of use;
FIG. 7 is a left side view similar to FIG. 2 but showing the same needle threader with the threading plate pivoted into the housing;
FIG. 8 is a right side view similar to FIG. 3 but showing the same needle threader with the threading plate pivoted into the housing;
FIG. 9 is a top plan view similar to FIG. 4 but showing the same needle threader with the threading plate pivoted into the housing; and,
FIG. 10 is a bottom view similar to FIG. 5 but showing the same needle threader with the threading plate pivoted into the housing.