When using keepinventory = true. If the player is killed in the process of drinking a potion or eating food then the potion or food item will be consumed while on the death screen. This allows potions and food to be wasted when trying to keep from dying in combat.

The drinking process should stop on death and the potion or food should not be consumed until the end of the drinking animation.

The following is based on a decompiled version of Minecraft 1.10 using MCP 9.30.

To fix this, add an if statement to check if the player is alive in onItemUseFinish before depleting the item.

	public ItemStack onItemUseFinish(ItemStack stack, World worldIn, EntityLivingBase entityLiving) 
	{
		if (entityLiving.isEntityAlive()) 
		{

		}
		
		return stack;
		
	}

	public ItemStack onItemUseFinish(ItemStack stack, World worldIn, EntityLivingBase entityLiving) 
	{
		EntityPlayer entityplayer = entityLiving instanceof EntityPlayer ? (EntityPlayer) entityLiving : null;

		if (entityplayer.isEntityAlive()) 
		{

		}
		
		return stack;
		
	}