Rimworld modded error

Exception filling window for WhatTheHack.TabWindowNew.MainTabWindow_Work_MechanoidsNew: System.NullReferenceException: Object reference not set to an instance of an object
  at WorkTab.PawnColumnWorker_WorkType.DoCell (UnityEngine.Rect rect, Verse.Pawn pawn, RimWorld.PawnTable table) [0x0001a] in <1047f5dc1d7a4966ba34328f27e10396>:0
  at WorkTab.PawnTable_PawnTableOnGUI.Prefix (RimWorld.PawnTable __instance, UnityEngine.Vector2 position, RimWorld.PawnTableDef ___def, UnityEngine.Vector2& ___scrollPosition) [0x00642] in <1047f5dc1d7a4966ba34328f27e10396>:0
  at (wrapper dynamic-method) RimWorld.PawnTable.RimWorld.PawnTable.PawnTableOnGUI_Patch1(RimWorld.PawnTable,UnityEngine.Vector2)
  at RimWorld.MainTabWindow_PawnTable.DoWindowContents (UnityEngine.Rect rect) [0x00020] in <99518a644a3e4a7ea3fde566568df84a>:0
  at RimWorld.MainTabWindow_Work.DoWindowContents (UnityEngine.Rect rect) [0x00000] in <99518a644a3e4a7ea3fde566568df84a>:0
  at Verse.Window.InnerWindowOnGUI (System.Int32 x) [0x001d3] in <99518a644a3e4a7ea3fde566568df84a>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
(wrapper dynamic-method) Verse.Log:Verse.Log.Error_Patch2 (string)
Verse.Window:InnerWindowOnGUI (int)
UnityEngine.GUI:CallWindowDelegate (UnityEngine.GUI/WindowFunction,int,int,UnityEngine.GUISkin,int,single,single,UnityEngine.GUIStyle)

Error #2:
Mouse position stack is not empty. There were more calls to BeginScrollView than EndScrollView. Fixing.
UnityEngine.StackTraceUtility:ExtractStackTrace ()
(wrapper dynamic-method) Verse.Log:Verse.Log.Error_Patch2 (string)
Verse.Widgets:EnsureMousePositionStackEmpty ()
(wrapper dynamic-method) Verse.Root:Verse.Root.Update_Patch1 (Verse.Root)
Verse.Root_Play:Update ()