Fix for incompatible magazine spawning in national guard camp

[hfox]

Summary

SUMMARY: Bugfixes "Correct magazine inside guns/monsters."

Purpose of change

I found a SCAR-L in the national guard camp, but when picking it up, the game crashed with weird messages. After examining the logs and savegame, I concluded that it contained the wrong magazine(scarhmag).
I also got errors about the W12B10 using incompatible magazines for their flamethrowers, roughly same conclusion.

Describe the solution

Setting the SCAR-L in the national guard itemgroup to spawn/drop with the correct magazine.
Setting the W12B10 to use napalm insted of gasoline for their flamethrower.

Describe alternatives you've considered

• Changing the gun to a SCAR-H and ammo drops to 7.62x51mm, would make some sense due to monster descriptions.
• Making the monsters drop their actual gun instead, but I need some guidance on how for that option.

Testing

edited, killed a few W11B10(dropping that itemgroup), and the SCAR-Ls did not crash the game.
edited, spawned a few W12B10, they burned me a lot.

Additional context