The colonist Choi was just successfully calmed down by another colonist. After she is no longer wandering in sadness, the game paused and popup this error:

Exception in SetupToils for pawn Choi driver=JobDriver_ActuallyRecover (toilIndex=-1) driver.job=(SnapOut_ActuallyRecoverJob (Job_2033570))
System.NullReferenceException: Object reference not set to an instance of an object
at SnapOut.JobDriver_ActuallyRecover+<MakeNewToils>d__1.MoveNext () [0x00052] in <e0da1d2f7f0e45fc98bb457bd2bbe3c5>:0
at Verse.AI.JobDriver.SetupToils () [0x00052] in <65f126dfb1e4464fa378d4b237f11a99>:0
Verse.Log:Error(String, Boolean)
Verse.AI.JobUtility:TryStartErrorRecoverJob(Pawn, String, Exception, JobDriver)
Verse.AI.JobDriver:SetupToils()
Verse.AI.Pawn_JobTracker:DMD<DMD<StartJob_Patch1>?-980577792::StartJob_Patch1>(Pawn_JobTracker, Job, JobCondition, ThinkNode, Boolean, Boolean, ThinkTreeDef, Nullable`1, Boolean, Boolean)
SnapOut.<>c__DisplayClass1_0:<MakeNewToils>b__0()
Verse.AI.JobDriver:TryActuallyStartNextToil()
Verse.AI.JobDriver:ReadyForNextToil()
Verse.AI.JobDriver:DriverTick()
Verse.AI.Pawn_JobTracker:JobTrackerTick()
Verse.Pawn:DMD<DMD<Tick_Patch1>?-1981927680::Tick_Patch1>(Pawn)
Verse.TickList:Tick()
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update()

It does not actually affect the gaming process, but I think you may be able to fix it.