"Exception while generating thing set: System.NullReferenceException: Object reference not set to an instance of an object
at RimWorld.StockGeneratorUtility+<TryMakeForStock>d__0.MoveNext () [0x00022] in <cdbd0ed5089a418da09b9a259f9dbd8f>:0
at VanillaBooksExpanded.Patch_TryMakeForStock+<Postfix>d__0.MoveNext () [0x000f0] in <88fab6adde9a4473924fd6e7225d8e41>:0
at RimWorld.StockGenerator_SingleDef+<GenerateThings>d__1.MoveNext () [0x0007b] in <cdbd0ed5089a418da09b9a259f9dbd8f>:0
at RimWorld.ThingSetMaker_TraderStock.Generate (RimWorld.ThingSetMakerParams parms, System.Collections.Generic.List`1[T] outThings) [0x000e4] in <cdbd0ed5089a418da09b9a259f9dbd8f>:0
at RimWorld.ThingSetMaker.Generate (RimWorld.ThingSetMakerParams parms) [0x00019] in <cdbd0ed5089a418da09b9a259f9dbd8f>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
RimWorld.ThingSetMaker:Generate (RimWorld.ThingSetMakerParams)
RimWorld.TradeShip:GenerateThings ()
RimWorld.IncidentWorker_OrbitalTraderArrival:TryExecuteWorker (RimWorld.IncidentParms)
(wrapper dynamic-method) RimWorld.IncidentWorker:RimWorld.IncidentWorker.TryExecute_Patch1 (RimWorld.IncidentWorker,RimWorld.IncidentParms)
Verse.DebugActionsMisc/<>c__DisplayClass5_0:<AddTradeShipOfKind>b__1 ()
Verse.Dialog_DebugOptionLister:DebugAction (string,System.Action,bool)
Verse.Dialog_DebugOptionListLister:DoListingItems ()
Verse.Dialog_OptionLister:DoWindowContents (UnityEngine.Rect)
Verse.Window:InnerWindowOnGUI (int)
UnityEngine.GUI:CallWindowDelegate (UnityEngine.GUI/WindowFunction,int,int,UnityEngine.GUISkin,int,single,single,UnityEngine.GUIStyle)
"