Scorched turfs are sometimes incorrect when map edited

### Testmerges

#5007: 'Project ARES TM Holder (v4)' by realforest2001 at commit 6c41b6abac #5392: 'Yautja Weapon Gimmicks, Round Two' by realforest2001 at commit f164a729d3 #5584: 'Jumping out of a dropship heading towards an LZ now throws your body at the ground, instead of deleting it.' by Contrabang at commit fec4de9955 #3633: 'Black Goo Patch' by realforest2001 at commit 9e7c29b685 #5401: 'M540-A Armored Recon Carrier' by Zonespace27 at commit d8e390ddbf #5432: 'Abomination rework and predator plasma rifle buff.' by InsaneRed at commit a7a2e82af3 #5657: 'Reactor changes' by BeagleGaming1 at commit 98c5e342ac

### Round ID

20949

### Description of the bug

Map var edited turfs can have the incorrect scorched state such as here on LV624:

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

In this case since there's no grass to scorch, it ultimately should not be scorchable.

Ultimately the var edits like this on the map probably should use a subtype rather than just edited.

However, another aspect that is funky is that the var scorched is defined to be treated like a bool; but its half used purely as a bool, and other times used to determine a mask to use. So likely the comment for the var is incorrect.

### How do we reproduce this bug?

1. Go to 146,102, 2 on LV624
2. Ignite the ground
3. Notice it suddenly turns to grass
4. Wait for fire to burn out
5. Repeat 1-2 once or twice more
6. Observe broken sprite

### 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)