What is the problem with this actually?

[sstareven]

When I played with my friend, I desynced.
And I found the red log, showing that:

System.ArgumentNullException: Argument cannot be null.
Parameter name: type
at System.Activator.CheckType (System.Type) <0x00095>
at System.Activator.CreateInstance (System.Type,bool) <0x00027>
at System.Activator.CreateInstance (System.Type) <0x0001e>
at RimWorld.IncidentDef.get_Worker () <0x00036>
at RimWorld.StorytellerComp/c__AnonStorey3.<>m__0 (RimWorld.IncidentDef) <0x00039>
at System.Linq.Enumerable/c__Iterator1D1<RimWorld.IncidentDef>.MoveNext () <0x0016b> at Verse.GenCollection.TryRandomElementByWeight<RimWorld.IncidentDef> (System.Collections.Generic.IEnumerable1<RimWorld.IncidentDef>,System.Func`2<RimWorld.IncidentDef, single>,RimWorld.IncidentDef&) <0x00787>
at RimWorld.StorytellerComp_CategoryMTB/c__Iterator0.MoveNext () <0x00272>
at RimWorld.Storyteller/c__Iterator1.MoveNext () <0x0043b>
at RimWorld.Storyteller/c__Iterator0.MoveNext () <0x001ce>
at (wrapper dynamic-method) RimWorld.Storyteller.StorytellerTick_Patch1 (object) <0x0011d>
at (wrapper dynamic-method) Verse.TickManager.DoSingleTick_Patch1 (object) <0x00630>

How to fix it? Is it caused by some mod conflicts?