The ornamental design for a flashmodifier, as shown and described.
FIG. 1 is a top perspective view of a flash modifier showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a right side view thereof, the left side view is a mirror image thereof; and,
FIG. 7 is a right side view of another embodiment of the flash modifier in which the circular feature near the top of the flash modifier is concave instead of convex as shown in FIG. 6.
The broken lines in the drawings depict portions of the flash modifier that form no part of the claimed design.