Guard Infinite Zoop subsystem updates

[kyleclarktech]

Summary

This hardens Infinite Zoop's build-gun subsystem update path against missing world/subsystem/hologram state.

The crash seen in Satisfactory 1.2 (CL 491125, SML 3.12.0) happens through:

AInfiniteZoopSubsystem::SetPublicZoopAmount()
FInfiniteZoopModule::SetSubsystemZoopAmounts()
FInfiniteZoopModule::BGSecondaryFire()
UFGBuildGunState::SecondaryFire
AFGBuildGun::Input_SecondaryFire()

In affected runtime logs, the native Infinite Zoop module loads, but /Script/InfiniteZoop.InfiniteZoopSubsystem is not registered. SetSubsystemZoopAmounts() then assumes the subsystem actor exists and calls SetPublicZoopAmount() through a null pointer, producing an access violation at address 0x00000000000002c0.

Changes

• Return early from SetSubsystemZoopAmounts() if the world, hologram, subsystem actor manager, Infinite Zoop subsystem, or construction instigator is unavailable.
• Reuse the validated construction instigator for all SetPublicZoopAmount() calls.
• Make SetPublicZoopAmount() release the provided critical section before returning when owner is null.
• Avoid leaving the critical section locked in the vertical zoop branch by using a single write/update/unlock path.

Validation

• Ran git diff --check.
• Inspected the reported crash path against the guarded code path.
• Could not compile locally because this checkout does not include a configured Satisfactory/Unreal mod build environment.

Notes

This prevents the native hook from crashing when the subsystem is missing. It does not by itself explain why the Infinite Zoop world module/subsystem is sometimes absent after the 1.2 GameFeature/SML 3.12 migration, so there may still be a packaging or asset-registration issue to investigate separately.

[mklierman]

Looks good so far. Let me know when you're ready for a full review