Custom Incinerator fuel: Oxygen sometimes behaves oddly at different u/ts

### Testmerges

#4842: '/tg/ Status Effects Part 2 - datum, KD, KO, Stuns' by fira at commit 6fa7d179f6 #5130: 'Armor Light Buff for Heavy/Medium/Leader armor' by Nanu308 at commit 0967f9b459 #5157: 'adds a medal viewer' by harryob at commit c7e273713a

### Round ID

19897

### Description of the bug

https://youtu.be/X8sUONx9-Q8?si=cWiWQdG9PZNsR45A

Oddity occurs once at :40

https://youtu.be/4QL1hHQejHw

Happened some more late on twice in a row- seems kinda random but maybe it's a rounding error or something with the amount of fuel left inside the canister.

### What's the difference with what should have happened?

Shoulda been oxygen fire only

### How do we reproduce this bug?

1. Fill incin tanks with oxygen
2. Cycle through the various u/t amounts
3. Seemingly randomly it may put out regular incinerator fire
...

### Issue Bingo

- [X] Issue could be reproduced at least once
- [X] Issue happened in a recent (less than 7 days ago) round
- [X] Couldn't find an existing issue about this (https://github.com/cmss13-devs/cmss13/issues)