Fix a bug that could freeze up a weapon and even the simulation

[Garanas]

Description of the proposed changes

Related to this forum post and this Discord post.

Weapons now properly use the AttackGroundTries field because of #6277. For the average unit this is fine, but for bombers and specifically bombers with multiple projectiles per salvo it introduced an unusual problem: the first projectile would aim at the current target. All remaining projectiles may aim at the next target. This doesn't apply to all bombers, but in particular the UEF Tech 1 bomber (Scorcher) fell victim to this bug.

When the bug happens we end up in an unstable state. To the user this would show as:

• (1) A bomber with a weapon that is no longer functional.
• (2) The simulation freezes up.

These issues are related to how we re-compute the (vertical) bomb trajectory in Lua. We do this in Lua to fix an engine bug where bombers would constantly miss their target. For a salvo the code assumes that the ground target does not suddenly shift as the salvo is being processed. This is a safe assumption as any normal interrupt would also cancel the salvo. But now that the engine can use the AttackGroundTries field again it is suddenly very possible that this happens throughout the salvo. And as a result the computations are all messed up. And because of that we try to get the square root of a negative number. This imaginary number does not exist in the real world and since we simulate the real world here (ha) the game returns an invalid number: -1.#ND.

This introduces all sorts of problems. One of them is (1). The other is (2) as we pass the invalid number to SetBallisticAcceleration. The moment that happens the simulation freezes.

Testing done on the proposed changes

Spawn in various bombers and make them bomb random patches of ground.

Additional context

The behavior of the Scorcher is consistent between FAForever and Steam - for some odd reason the Janus works as expected and the Scorcher appears to switch targets too soon. Could it be because it is the primary weapon of the Scorcher?

Checklist

• Changes are annotated, including comments where useful
• Changes are documented in the changelog for the next game version

[ErikMekkes]

Resolves the bugged weapon fire state for the scorcher due to target switching after 3 attempts on the current target 👍

some issues with retargeting for ground attacks remain but were not as critical

• trajectory issues for zeus, scorcher, possibly others salvo projectiles on 3rd attack
• skipped attack but with reload 'penalty' for 3rd salvo of Janus, Ravager, possibly others