Have been getting this error log every 10~20 seconds for a week. Any idea why?

Exception in BreadthFirstTraverse: System.NullReferenceException: Object reference not set to an instance of an object
at BabiesAndChildren.Harmony.DubsBadHygienePatches.HasJobOnThingPostfix (Verse.Pawn pawn, Verse.Thing t, System.Boolean& __result) [0x0003a] in <213d62fc0ce64d7a822063c956e167c1>:0
at (wrapper dynamic-method) DubsBadHygiene.WorkGiver_washPatient.DubsBadHygiene.WorkGiver_washPatient.HasJobOnThing_Patch1(DubsBadHygiene.WorkGiver_washPatient,Verse.Pawn,Verse.Thing,bool)
at RimWorld.JobGiver_Work+<>c__DisplayClass3_1.<TryIssueJobPackage>b__0 (Verse.Thing t) [0x00013] in <d243303f714d4dc48680ccaecd2f594e>:0
at Verse.GenClosest+<>c__DisplayClass4_0.<RegionwiseBFSWorker>b__1 (Verse.Region r) [0x000f7] in <d243303f714d4dc48680ccaecd2f594e>:0
at Verse.RegionTraverser+BFSWorker.BreadthFirstTraverseWork (Verse.Region root, Verse.RegionEntryPredicate entryCondition, Verse.RegionProcessor regionProcessor, System.Int32 maxRegions, Verse.RegionType traversableRegionTypes) [0x00054] in <d243303f714d4dc48680ccaecd2f594e>:0
at Verse.RegionTraverser.BreadthFirstTraverse (Verse.Region root, Verse.RegionEntryPredicate entryCondition, Verse.RegionProcessor regionProcessor, System.Int32 maxRegions, Verse.RegionType traversableRegionTypes) [0x00044] in <d243303f714d4dc48680ccaecd2f594e>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
(wrapper dynamic-method) Verse.Log:Verse.Log.Error_Patch2 (string)
Verse.RegionTraverser:BreadthFirstTraverse (Verse.Region,Verse.RegionEntryPredicate,Verse.RegionProcessor,int,Verse.RegionType)
Verse.GenClosest:RegionwiseBFSWorker (Verse.IntVec3,Verse.Map,Verse.ThingRequest,Verse.AI.PathEndMode,Verse.TraverseParms,System.Predicate`1<Verse.Thing>,System.Func`2<Verse.Thing, single>,int,int,single,int&,Verse.RegionType,bool)
Verse.GenClosest:ClosestThingReachable (Verse.IntVec3,Verse.Map,Verse.ThingRequest,Verse.AI.PathEndMode,Verse.TraverseParms,single,System.Predicate`1<Verse.Thing>,System.Collections.Generic.IEnumerable`1<Verse.Thing>,int,int,bool,Verse.RegionType,bool)
(wrapper dynamic-method) RimWorld.JobGiver_Work:RimWorld.JobGiver_Work.TryIssueJobPackage_Patch1 (RimWorld.JobGiver_Work,Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_PrioritySorter:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Priority:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Tagger:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Subtree:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Priority:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Conditional:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
Verse.AI.ThinkNode_Priority:TryIssueJobPackage (Verse.Pawn,Verse.AI.JobIssueParams)
(wrapper dynamic-method) Verse.AI.Pawn_JobTracker:Verse.AI.Pawn_JobTracker.DetermineNextJob_Patch4 (Verse.AI.Pawn_JobTracker,Verse.ThinkTreeDef&)
Verse.AI.Pawn_JobTracker:TryFindAndStartJob ()
(wrapper dynamic-method) Verse.AI.Pawn_JobTracker:Verse.AI.Pawn_JobTracker.EndCurrentJob_Patch2 (Verse.AI.Pawn_JobTracker,Verse.AI.JobCondition,bool,bool)
(wrapper dynamic-method) Verse.AI.Pawn_JobTracker:Verse.AI.Pawn_JobTracker.JobTrackerTick_Patch0 (Verse.AI.Pawn_JobTracker)
(wrapper dynamic-method) Verse.Pawn:Verse.Pawn.Tick_Patch4 (Verse.Pawn)
Verse.TickList:Tick ()
(wrapper dynamic-method) Verse.TickManager:Verse.TickManager.DoSingleTick_Patch2 (Verse.TickManager)
Verse.TickManager:TickManagerUpdate ()
(wrapper dynamic-method) Verse.Game:Verse.Game.UpdatePlay_Patch3 (Verse.Game)
Verse.Root_Play:Update ()