Hotfix 1843

[In-Game Build Version 1843]

Fix: An issue where the Cleveland in the combat tutorial was not taking damage.

Fix: An issue where the Cleveland in the combat tutorial might move incorrectly.

Fix: A NullReferenceException error that could occur upon shell impact if the hit collider lacked a PartAttribute.

Fix: A rendering error with the horizon line when using Skybox Mode.

Fix: An issue with the unlocking of secondary objective rewards in Career Level 2-1.

Fix: Several dialogue text errors in Career Level 2-1.

Adjustment: Switched mod part validation to an "on-demand" system to reduce validation time, and improved the error reporting mechanism for loading mod parts.