* Fix two gas assertion runtimes (#53718)
/datum/gas_mixture/proc/remove(amount) has a code path that can return null.
All the code following the runtimes assume some bit of gas_mixture was actually removed at all. No need to trigger this code if there's no gas_mixture removed, can early return instead.
* Fix two gas assertion runtimes
Co-authored-by: Timberpoes <silent_insomnia_pp@hotmail.co.uk>