Return prefub with empty animator.

IndexOutOfRangeException: Index was outside the bounds of the array.
Spine.Unity.Editor.SkeletonBaker.ParseRotateTimeline (Spine.Skeleton skeleton, Spine.RotateTimeline timeline, UnityEngine.AnimationClip clip) (at Assets/Spine/Editor/spine-unity/Editor/Windows/SkeletonBaker.cs:1224)
Spine.Unity.Editor.SkeletonBaker.ExtractAnimation (System.String name, Spine.SkeletonData skeletonData, System.Collections.Generic.Dictionary2[TKey,TValue] slotLookup, System.Boolean bakeIK, UnityEngine.SendMessageOptions eventOptions, UnityEngine.AnimationClip clip) (at Assets/Spine/Editor/spine-unity/Editor/Windows/SkeletonBaker.cs:790) Spine.Unity.Editor.SkeletonBaker.BakeToPrefab (Spine.Unity.SkeletonDataAsset skeletonDataAsset, Spine.ExposedList1[T] skins, System.String outputPath, System.Boolean bakeAnimations, System.Boolean bakeIK, UnityEngine.SendMessageOptions eventOptions) (at Assets/Spine/Editor/spine-unity/Editor/Windows/SkeletonBaker.cs:242)
Spine.Unity.Editor.SkeletonBakingWindow.OnGUI () (at Assets/Spine/Editor/spine-unity/Editor/Windows/SkeletonBakingWindow.cs:159)
UnityEditor.HostView.OldOnGUI () (at <25e9afc147634a5ca855ab83fab425dd>:0)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUIRaw (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.IMGUIContainer.HandleEvent (UnityEngine.UIElements.EventBase evt) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.CallbackEventHandler.HandleEventAtTargetPhase (UnityEngine.UIElements.EventBase evt) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.MouseCaptureDispatchingStrategy.DispatchEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.ApplyDispatchingStrategies (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, System.Boolean imguiEventIsInitiallyUsed) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEventQueue () (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.OpenGate () (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcherGate.Dispose () (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at <270875aa25744a3b8d4f4ee5dc922b56>:0)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at <6ddf8eac3856492ab1b8cf42618915cc>:0)