System.NullReferenceException: Object reference not set to an instance of an object
at MoreFactionInteraction.World_Incidents.SitePartWorker_MigratoryHerd/<>c__DisplayClass3_0.<TryFindAnimalKind>b__0 (Verse.PawnKindDef) <0x00025>
at System.Linq.Enumerable/<CreateWhereIterator>c__Iterator1D`1<Verse.PawnKindDef>.MoveNext () <0x0016b>
at Verse.GenCollection.TryRandomElementByWeight<Verse.PawnKindDef> (System.Collections.Generic.IEnumerable`1<Verse.PawnKindDef>,System.Func`2<Verse.PawnKindDef, single>,Verse.PawnKindDef&) <0x00a30>
at Verse.GenCollection.RandomElementByWeightWithFallback<Verse.PawnKindDef> (System.Collections.Generic.IEnumerable`1<Verse.PawnKindDef>,System.Func`2<Verse.PawnKindDef, single>,Verse.PawnKindDef) <0x00063>
at MoreFactionInteraction.World_Incidents.SitePartWorker_MigratoryHerd.TryFindAnimalKind (int,Verse.PawnKindDef&) <0x0015d>
at MoreFactionInteraction.World_Incidents.SitePartWorker_MigratoryHerd.GenerateDefaultParams (RimWorld.Planet.Site,single) <0x0006d>
at RimWorld.Planet.SiteMaker.MakeSite (RimWorld.SiteCoreDef,System.Collections.Generic.IEnumerable`1<RimWorld.SitePartDef>,int,RimWorld.Faction,bool,System.Nullable`1<single>) <0x0045c>
at RimWorld.Planet.SiteMaker.MakeSite (RimWorld.SiteCoreDef,RimWorld.SitePartDef,int,RimWorld.Faction,bool,System.Nullable`1<single>) <0x00073>
at MoreFactionInteraction.World_Incidents.IncidentWorker_HuntersLodge.TryExecuteWorker (RimWorld.IncidentParms) <0x0014b>
at (wrapper dynamic-method) RimWorld.IncidentWorker.TryExecute_Patch1 (object,RimWorld.IncidentParms) <0x0005c>
at RimWorld.Storyteller.TryFire (RimWorld.FiringIncident) <0x0008e>
at RimWorld.IncidentQueue.IncidentQueueTick () <0x000c4>
at RimWorld.Storyteller.StorytellerTick () <0x0002f>
at Verse.TickManager.DoSingleTick () <0x00610>

Verse.Log:Error(String, Boolean)
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update_Patch1(Object)

More info at Ludeon forum: https://ludeon.com/forums/index.php?topic=49034.0