For some reason saving and reloading fixes the problem.
Error log next:
Root level exception in OnGUI(): System.NullReferenceException: Object reference not set to an instance of an object
at Numbers.WorldComponent_Numbers+<>c.<.cctor>b__8_5 (Verse.Pawn pawn) [0x00000] in <9ff61b29a7ab468ba28486fbf1f24cff>:0
at Numbers.MainTabWindow_Numbers+<>c__DisplayClass24_0.<get_Pawns>b__0 (System.Func`2[T,TResult] validator) [0x0000c] in <9ff61b29a7ab468ba28486fbf1f24cff>:0
at System.Linq.Enumerable.All[TSource] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] predicate) [0x0002c] in <351e49e2a5bf4fd6beabb458ce2255f3>:0
at Numbers.MainTabWindow_Numbers+<get_Pawns>d__24.MoveNext () [0x0006a] in <9ff61b29a7ab468ba28486fbf1f24cff>:0
at System.Collections.Generic.List`1[T].InsertRange (System.Int32 index, System.Collections.Generic.IEnumerable`1[T] collection) [0x000db] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Collections.Generic.List`1[T].AddRange (System.Collections.Generic.IEnumerable`1[T] collection) [0x00000] in <eae584ce26bc40229c1b1aa476bfa589>:0
at RimWorld.PawnTable.RecachePawns () [0x0001c] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.PawnTable.RecacheIfDirty () [0x00010] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.PawnTable.get_Size () [0x00000] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainTabWindow_PawnTable.get_RequestedTabSize () [0x0000e] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainTabWindow.get_InitialSize () [0x00000] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at Verse.Window.SetInitialSizeAndPosition () [0x00000] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainTabWindow.SetInitialSizeAndPosition () [0x00000] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at Verse.Window.Notify_ResolutionChanged () [0x00000] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainTabWindow_PawnTable.Notify_ResolutionChanged () [0x0000c] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at Numbers.MainTabWindow_NumbersWildLife.PostOpen () [0x0003b] in <9ff61b29a7ab468ba28486fbf1f24cff>:0
at Verse.WindowStack.Add (Verse.Window window) [0x0003a] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainTabsRoot.ToggleTab (RimWorld.MainButtonDef newTab, System.Boolean playSound) [0x0006b] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainButtonWorker_ToggleTab.Activate () [0x00005] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainButtonWorker.InterfaceTryActivate () [0x0008d] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainButtonWorker.DoButton (UnityEngine.Rect rect) [0x000ee] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainButtonsRoot.DoButtons () [0x00119] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.MainButtonsRoot.MainButtonsOnGUI () [0x0000e] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at RimWorld.UIRoot_Play.UIRootOnGUI () [0x00037] in <b3561b1be0664abaaf1e5c4602ec1431>:0
at (wrapper dynamic-method) Verse.Root.Verse.Root.OnGUI_Patch1(Verse.Root)
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
(wrapper dynamic-method) Verse.Root:Verse.Root.OnGUI_Patch1 (Verse.Root)