Fix aircraft stalling for invalid targets

[tjk-ws]

#21451 introduced a regression that helicopters in TD lost their targets when out of ammo. The checks for armaments being paused (as is the usual ammo case) versus invalid are separated, so the activity is completed only in the latter case.

[PunkPun]

This implementation is still bogus. Sorry, #21451 should be reverted and instead the correct behaviour would be to cancel if all armaments are disabled instead of paused

It seems the scenario for IsTraitDisabled is not handled at all in FlyAttack

[tjk-ws]

This implementation is still bogus. Sorry, #21451 should be reverted and instead the correct behaviour would be to cancel if all armaments are disabled instead of paused

It seems the scenario for IsTraitDisabled is not handled at all in FlyAttack

Added, though the valid target check is still needed because mods may change the targets' targetability during battles.

[PunkPun]

shouldn't a rearmable unit cancel its activity when the target is invalid as well? And when armaments are disabled?

[tjk-ws]

shouldn't a rearmable unit cancel its activity when the target is invalid as well? And when armaments are disabled?

My understanding is that it would have passed the first check on paused armaments. Then it would be caught by the invalid target/armament check like any non-rearmable unit

[PunkPun]

What about a case where a unit has its armaments paused but the target is also invalid? Or if the target is valid only for the armamants that are paused and not all armamanets are paused?

[tjk-ws]

Updated EDIT: seems to still stall for a case of a Yak with additional Colt45 with no ammo requirement force-firing a phase transport with default targetable trait disabled when cloaking

[tjk-ws]

This second cause of stalling I've found seems to be unrelated - if all of an actor's targetable traits are disabled, target.IsValidFor() returns false and the check for a true useLastVisibleTarget runs instead. Nothing stops from the aircraft from moving to the target but it will not actually perform an attack run. However a targetable trait which does not need to correspond to any of the aircraft's weapons but which will always be enabled seems to prevent this.

When this happens target.Type is always Actor and lastVisibleMaximumRange is always 0 (because attackAircraft.GetMaximumRangeVersusTarget actually uses the weapons, which can't attack the target), if those are good starting points for a check.

[tjk-ws]

For the sake of consistency and limiting the scope of the commit, I've taken the approach in base AttackFollow where the activity is always completed in the zero range case, the behavior of cancelling on targets becoming untargetable is consistent with e.g. ground turreted units.

[PunkPun]

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