Not sure it is the same bug, or similar, but I thought I would add here instead of a new thread:
1. Not using multi platform
2. Creating a new animation collection, then adding a new clip
3. Then, deleting the very first and only frame (from the timeline, pressing DEL)
I then get out of range error, and have nothing to do other than close it, and reopen.
The error:
ArgumentOutOfRangeException: Argument is out of range.
Parameter name: index
System.Collections.Generic.List`1[tk2dEditor.SpriteAnimationEditor.ClipEditor+FrameGroup].get_Item (Int32 index)
tk2dEditor.SpriteAnimationEditor.AnimOperatorUtil.NewFrameGroup (System.Collections.Generic.List`1 frameGroups, Int32 selectedFrameGroup) (at Assets/TK2DROOT/tk2d/Editor/Sprites/SpriteAnimationEditor/tk2dSpriteAnimationAnimOp.cs:48)
tk2dEditor.SpriteAnimationEditor.TimelineEditor.DrawFrameGroups (Int32 controlId, Rect frameGroupRect, .tk2dSpriteAnimationClip clip, System.Collections.Generic.List`1 frameGroups, Single clipTimeMarker) (at Assets/TK2DROOT/tk2d/Editor/Sprites/SpriteAnimationEditor/tk2dSpriteAnimationClipTimelineEditor.cs:230)
tk2dEditor.SpriteAnimationEditor.TimelineEditor.Draw (Int32 windowWidth, .tk2dSpriteAnimationClip clip, System.Collections.Generic.List`1 frameGroups, Single clipTimeMarker) (at Assets/TK2DROOT/tk2d/Editor/Sprites/SpriteAnimationEditor/tk2dSpriteAnimationClipTimelineEditor.cs:158)
tk2dEditor.SpriteAnimationEditor.ClipEditor.Draw (Int32 windowWidth) (at Assets/TK2DROOT/tk2d/Editor/Sprites/SpriteAnimationEditor/tk2dSpriteAnimationClipEditor.cs:564)
tk2dSpriteAnimationEditorPopup.OnGUI () (at Assets/TK2DROOT/tk2d/Editor/Sprites/SpriteAnimationEditor/tk2dSpriteAnimationEditorPopup.cs:480)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture)