Exception loading mission in builder

[tomf]

I spent yesterday creating a mission in the mission builder. When I come to try and load it this morning I get an error in the console and an exception in the logs

IndexOutOfRangeException: Array index is out of range.
  at PartCrewManifest.FromConfigNode (.ConfigNode node, .VesselCrewManifest v) [0x00000] in <filename unknown>:0
  at VesselCrewManifest.FromConfigNode (.ConfigNode craftNode) [0x00000] in <filename unknown>:0
  at Expansions.Missions.Runtime.MissionSystem.ValidateCrewAssignments (Expansions.Missions.Mission mission) [0x00000] in <filename unknown>:0
  at Expansions.Missions.Editor.MissionEditorLogic.MissionToLoadSelected (System.String fullPath) [0x00000] in <filename unknown>:0
  at Expansions.Missions.Editor.MissionsBrowserDialog.onButtonLoad () [0x00000] in <filename unknown>:0
  at UnityEngine.Events.InvokableCall.Invoke () [0x00000] in <filename unknown>:0
  at UnityEngine.Events.UnityEvent.Invoke () [0x00000] in <filename unknown>:0
  at UnityEngine.UI.Button.Press () [0x00000] in <filename unknown>:0
  at UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) [0x00000] in <filename unknown>:0
  at UnityEngine.EventSystems.ExecuteEvents.Execute (IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) [0x00000] in <filename unknown>:0
  at UnityEngine.EventSystems.ExecuteEvents.Execute[IPointerClickHandler] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.EventFunction`1 functor) [0x00000] in <filename unknown>:0
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
UnityEngine.EventSystems.ExecuteEvents:Execute(GameObject, BaseEventData, EventFunction`1)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMousePress(MouseButtonEventData)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMouseEvent(Int32)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMouseEvent()
UnityEngine.EventSystems.StandaloneInputModule:Process()
UnityEngine.EventSystems.EventSystem:Update()