Why is my game crashing?

[PetePablo]

NullReferenceException: Object reference not set to an instance of an object

SaveLoadRoot.SaveWithoutTransform (System.IO.BinaryWriter writer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveLoadRoot.Save (System.IO.BinaryWriter writer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveManager.Write (Tag key, System.Collections.Generic.List`1[T] value, System.IO.BinaryWriter writer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveManager.Save (System.IO.BinaryWriter writer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveLoader.Save (System.IO.BinaryWriter writer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveLoader.Save (System.String filename, System.Boolean isAutoSave, System.Boolean updateSavePointer) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveScreen.DoSave (System.String filename) (at <3d436e4ec1d5455793674ec559b0cc77>:0)
SaveScreen+<>c__DisplayClass9_0.<Save>b__0 () (at <3d436e4ec1d5455793674ec559b0cc77>:0)
ConfirmDialogScreen.OnSelect_OK () (at <3d436e4ec1d5455793674ec559b0cc77>:0)
KButton.SignalClick (KKeyCode btn) (at <3ca21dc18eae422d87255277091f8593>:0)
KButton.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at <3ca21dc18eae422d87255277091f8593>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at <e9635660f69b4d9d84c085aeda3be353>:0)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at <e9635660f69b4d9d84c085aeda3be353>:0)
UnityEngine.EventSystems.EventSystem:Update()

Build: U51-600112-SD