Screen capture of the event happening: https://gfycat.com/ApprehensiveInconsequentialAmethystgemclam
I am attempting to familiarize myself with the Unity Inverse Kinematics (IK) system, and so opened the avatar associated with the Ethan character in the standard assets. It lets me use the sliders in the "Muscle Group Settings" section, but if I attempt to move any of the sliders in the "Per-Muscle" settings, Unity throws a Null Reference Exception then stops updating the Scene window. The "Game" window continues to update, but is too small / far away for me to use as a preview mechanic.
I've tried restarting unity and reloading the project, to no avail.
Here's the exact error:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.AvatarMuscleEditor.DrawMuscleHandle (UnityEngine.Transform t, Int32 humanId) (at C:/buildslave/unity/build/Editor/Mono/Inspector/Avatar/AvatarMuscleEditor.cs:1021)
UnityEditor.AvatarMuscleEditor.OnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/Inspector/Avatar/AvatarMuscleEditor.cs:1126)
UnityEditor.AvatarEditor.OnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/Inspector/Avatar/AvatarEditor.cs:464)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.SceneView.CallOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2605)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1910)
UnityEditor.SceneView.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1757)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:295)
UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:288)
UnityEditor.HostView.InvokeOnGUI (Rect onGUIPosition) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:255)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)
