Bug report: Torracat's Gritty Claw

I used Torracat's Gritty Claw and, in the next turn, my opponent used Giratina V's Shred to attack. My Torracat was knocked out instead of survived with 10 HP. This must be bug. It said in Shred that "This attack's damage isn't affected by any effects on your opponent's Active Pokemon." However, I was not affecting its damage. My Torracat was technically knocked out first, but then it survived because of the effect on myself not any effect on Giratina. Please fix this.