spawn BigSandGrub issue

[woutkolkman]

Steps to reproduce:

1. Spawn a big sandgrub with spawn BigSandGrub.
2. Move to a few different rooms.
3. Make sure the room with the big sandgrub is unloaded via devtools.
4. Move back until the room with the big sandgrub is reloaded.

The game crashes with issues related to the big sandgrub.

I did have a pull request ready with a different implementation for spawning big sandgrubs, but that involved the sandgrub falling out of the room when the room reloads. It didn't crash the game though xP

Watcher.BigSandGrubNeck.Update () (at <477ce972de094f10bdadd556875c57af>:0)
Watcher.SandGrub.UpdateTentacle () (at <477ce972de094f10bdadd556875c57af>:0)
Watcher.SandGrub.Update (System.Boolean eu) (at <477ce972de094f10bdadd556875c57af>:0)
(wrapper dynamic-method) Room.DMD<Room::Update>(Room)
(wrapper dynamic-method) RainWorldGame.DMD<RainWorldGame::Update>(RainWorldGame)
(wrapper dynamic-method) MainLoopProcess.DMD<MainLoopProcess::RawUpdate>(MainLoopProcess,single)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Trampoline<MainLoopProcess::RawUpdate>?-1881758720(MainLoopProcess,single)
ScrollFix.Plugin.MainLoopProcess_RawUpdate (On.MainLoopProcess+orig_RawUpdate orig, MainLoopProcess self, System.Single dt) (at D:/Projects/Rain World Modding/CS Projects/RainWorld-ScrollFix/src/Plugin.cs:37)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Hook<MainLoopProcess::RawUpdate>?853994240(MainLoopProcess,single)
(wrapper dynamic-method) RainWorldGame.DMD<RainWorldGame::RawUpdate>(RainWorldGame,single)
ProcessManager.Update (System.Single deltaTime) (at <477ce972de094f10bdadd556875c57af>:0)
(wrapper dynamic-method) RainWorld.DMD<RainWorld::Update>(RainWorld)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Trampoline<RainWorld::Update>?-1336561664(RainWorld)
RainWorldTryCatch.RainWorldTryCatchPlugin.RainWorldUpdate (On.RainWorld+orig_Update orig, RainWorld self) (at <1828a154960541f185fd1181ef4110cd>:0)
UnityEngine.Debug:LogException(Exception)
RainWorldTryCatch.RainWorldTryCatchPlugin:RainWorldUpdate(orig_Update, RainWorld)
MonoMod.Utils.DynamicMethodDefinition:Hook<RainWorld::Update>?-2047977856(RainWorld)
MonoMod.Utils.DynamicMethodDefinition:Trampoline<RainWorld::Update>?1117293568(RainWorld)
BeastMaster.BeastMaster:RainWorldOnUpdate(orig_Update, RainWorld) (at /home/master/Coding/CSharp/Rain World/BestMaster/BeastMasterUpdate.cs:46)
MonoMod.Utils.DynamicMethodDefinition:Hook<RainWorld::Update>?770316544(RainWorld)```