fix(SDK): prevent crash using simulator prefab
fix(SDK): prevent crash using simulator prefab

The simulator prefab had not been updated to use the new
`Neck` and distance grab mechanic so it would cause a crash
in a new scene. The example scenes worked because the SDK Setup
prefab had been updated already.

virror/VRTK,mattboy64/SteamVR_Unity_Toolkit,red-horizon/VRTK,TMaloteaux/SteamVR_Unity_Toolkit,thestonefox/VRTK,gpvigano/VRTK,adamjweaver/VRTK,thestonefox/SteamVR_Unity_Toolkit,gpvigano/SteamVR_Unity_Toolkit,Fulby/VRTK,Innoactive/IA-unity-VR-toolkit-VRTK,gomez-addams/SteamVR_Unity_Toolkit