Trenchmaster's Immunity Breaking Blood Bag Mechanics

[Raw-air]

Describe the bug

Hi author, your dedicated bug reporter is here again
There is a small but serious bug. Since Trenchmaster is immune to damage, when using a blood bag to draw blood, the user doesn't take damage and even receives a free blood bag for healing. When using an Australium MK 3 with a blood bag, it deducts from the shield instead of the health, and I'm not sure if the latter counts as a bug. However, the fact that Trenchmaster can still use blood bags and draw blood without taking damage is too much.