The ornamental design for a flashhider, as shown and described herein.
FIG. 1 is a perspective front view of the flash hider, taken from a top-left angle in accordance with my invention;
FIG. 2 is a perspective front view thereof, taken from a bottom-left angle of FIG. 1;
FIG. 3 is a perspective front view thereof, taken from a top-right angle of FIG. 1;
FIG. 4 is a perspective front view thereof, taken from a bottom-right angle of FIG. 1;
FIG. 5 is a left side view thereof;
FIG. 6 is a right view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof;
FIG. 9 is a front view thereof; and,
FIG. 10 is a back view thereof.
The surface indicia of parallel lines also form no part of the claimed design and are merely surface shading. Furthermore, dashed lines form no part of the claimed design.