Stock OrbitalConstructionContract will softlock the game and brick the save if generated for a body that no longer exists

[JonnyOThan]

This is definitely user error for removing a planet pack, but....

If OrbitalConstructionContract is generated in the save file referring to a body that no longer exists, the save will load but then throw exceptions when saved, which can trap you in certain buildings.

[EXC 22:04:28.093] NullReferenceException: Object reference not set to an instance of an object
    Contracts.Templates.OrbitalConstructionContract.OnSave (ConfigNode node) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    Contracts.Contract.Save (ConfigNode node) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    Contracts.ContractSystem.OnSave (ConfigNode gameNode) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    ScenarioModule.Save (ConfigNode node) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    ProtoScenarioModule..ctor (ScenarioModule module) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    ScenarioRunner.UpdateModules () (at <4b449f2841f84227adfaad3149c8fdba>:0)
    ScenarioRunner.GetUpdatedProtoModules () (at <4b449f2841f84227adfaad3149c8fdba>:0)
    Game.Updated (GameScenes startSceneOverride) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    GamePersistence.SaveGame (System.String saveFileName, System.String saveFolder, SaveMode saveMode, GameScenes startScene) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    GamePersistence.SaveGame (System.String saveFileName, System.String saveFolder, SaveMode saveMode) (at <4b449f2841f84227adfaad3149c8fdba>:0)
    KSP.UI.Screens.RDSceneSpawner.onRDDespawn () (at <4b449f2841f84227adfaad3149c8fdba>:0)
    EventVoid.Fire () (at <4b449f2841f84227adfaad3149c8fdba>:0)
    UnityEngine.DebugLogHandler:LogException(Exception, Object)
    ModuleManager.UnityLogHandle.InterceptLogHandler:LogException(Exception, Object)
    UnityEngine.Debug:LogException(Exception)
    EventVoid:Fire()
    KSP.UI.Screens.RDSceneDespawner:BtnExit()
    UnityEngine.EventSystems.EventSystem:Update()