Fixed out of bound writes in grain filter for non mod 8 video.

(cherry picked from commit 8473f0753678b6ddf507a0cd9f6043704464b0e7)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/video_filter/grain.c

@@ -241,7 +241,8 @@ static void PlaneFilter(filter_t *filter,
             if (w >= BLEND_SIZE && h >= BLEND_SIZE)
                 sys->blend(dstp, dst->i_pitch, srcp, src->i_pitch, noise);
             else
-                BlockBlend(dstp, dst->i_pitch, srcp, src->i_pitch, noise, w, h);
+                BlockBlend(dstp, dst->i_pitch, srcp, src->i_pitch, noise,
+                           __MIN(w, BLEND_SIZE), __MIN(h, BLEND_SIZE));
         }
     }
     if (sys->emms)