Steps to reproduce:
-Create new skeleton GameObject.
-Create child GameObject.
-Add BoneFollower component to child.
Spine runtime version (Jan 5, 2017). Unity 5.5.0p3
ArgumentException: Getting control 2's position in a group with only 2 controls when doing Repaint
Aborting
UnityEngine.GUILayoutGroup.GetNext () (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/LayoutGroup.cs:114)
UnityEngine.GUILayoutUtility.DoGetRect (Single minWidth, Single maxWidth, Single minHeight, Single maxHeight, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:421)
UnityEngine.GUILayoutUtility.GetRect (Single minWidth, Single maxWidth, Single minHeight, Single maxHeight, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:410)
UnityEditor.EditorGUILayout.GetToggleRect (Boolean hasLabel, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:7517)
UnityEditor.PropertyHandler.OnGUILayout (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, Boolean includeChildren, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/ScriptAttributeGUI/PropertyHandler.cs:191)
UnityEditor.EditorGUILayout.PropertyField (UnityEditor.SerializedProperty property, UnityEngine.GUIContent label, Boolean includeChildren, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:7478)
UnityEditor.EditorGUILayout.PropertyField (UnityEditor.SerializedProperty property, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:7460)
Spine.Unity.Editor.BoneFollowerInspector.OnInspectorGUI () (at Assets/spine-unity/Editor/BoneFollowerInspector.cs:151)
UnityEditor.InspectorWindow.DrawEditor (UnityEditor.Editor editor, Int32 editorIndex, Boolean rebuildOptimizedGUIBlock, System.Boolean& showImportedObjectBarNext, UnityEngine.Rect& importedObjectBarRect) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1236)
UnityEditor.DockArea😮nGUI()