This fixes heisenbug with slots amount being incorrect after backpack upgrade
Description: Ticking player
java.lang.RuntimeException: Slot 9 not in valid range - [0,9)
at net.minecraftforge.items.ItemStackHandler.validateSlotIndex(ItemStackHandler.java:214)
at net.minecraftforge.items.ItemStackHandler.getStackInSlot(ItemStackHandler.java:73)
at v0id.vsb.capability.Backpack$NBTItemHandler.getStackInSlot(Backpack.java:370)
at net.minecraftforge.items.SlotItemHandler.getStack(SlotItemHandler.java:73)
at net.minecraft.inventory.Container.detectAndSendChanges(Container.java:79)
at net.minecraft.entity.player.EntityPlayerMP.onUpdate(EntityPlayerMP.java:324)
at net.minecraft.world.World.updateEntityWithOptionalForce(World.java:1993)
at net.minecraft.world.WorldServer.updateEntityWithOptionalForce(WorldServer.java:832)
at net.minecraft.world.World.updateEntity(World.java:1955)
at net.minecraft.world.WorldServer.tickPlayers(WorldServer.java:642)
at net.minecraft.world.World.updateEntities(World.java:1734)
at net.minecraft.world.WorldServer.updateEntities(WorldServer.java:613)
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:767)
at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397)
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
at java.lang.Thread.run(Unknown Source)
This fixes heisenbug with slots amount being incorrect after backpack upgrade