possible bug with pool JobDriver

[Georodin]

Exception in JobDriver tick for pawn Garrett driver=JobDriver_GoSwimming (toilIndex=8)
System.NullReferenceException: Object reference not set to an instance of an object
  at DubsBadHygiene.JobDriver_GoSwimming+<>c__DisplayClass7_0.<MakeNewToils>b__0 () [0x00015] in <4971d1f5097749f9afaf0fe77629ebe1>:0 
  at (wrapper dynamic-method) Verse.AI.JobDriver.Verse.AI.JobDriver.DriverTick_Patch0(Verse.AI.JobDriver)
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.AI.JobUtility:TryStartErrorRecoverJob (Verse.Pawn,string,System.Exception,Verse.AI.JobDriver)
(wrapper dynamic-method) Verse.AI.JobDriver:Verse.AI.JobDriver.DriverTick_Patch0 (Verse.AI.JobDriver)
Verse.AI.Pawn_JobTracker:JobTrackerTick ()
Verse.Pawn:Tick ()
Verse.TickList:Tick ()
Verse.TickManager:DoSingleTick ()
Verse.TickManager:TickManagerUpdate ()
Verse.Game:UpdatePlay ()
Verse.Root_Play:Update ()

pool is 3/4 filled, occurred after reloading the game once

[Georodin]

Exception in JobDriver tick for pawn Poopy driver=JobDriver_GoSwimming (toilIndex=8)
System.NullReferenceException: Object reference not set to an instance of an object
  at DubsBadHygiene.JobDriver_GoSwimming+<>c__DisplayClass7_0.<MakeNewToils>b__0 () [0x00015] in <4971d1f5097749f9afaf0fe77629ebe1>:0 
  at (wrapper dynamic-method) Verse.AI.JobDriver.Verse.AI.JobDriver.DriverTick_Patch0(Verse.AI.JobDriver)
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.AI.JobUtility:TryStartErrorRecoverJob (Verse.Pawn,string,System.Exception,Verse.AI.JobDriver)
(wrapper dynamic-method) Verse.AI.JobDriver:Verse.AI.JobDriver.DriverTick_Patch0 (Verse.AI.JobDriver)
Verse.AI.Pawn_JobTracker:JobTrackerTick ()
Verse.Pawn:Tick ()
Verse.TickList:Tick ()
Verse.TickManager:DoSingleTick ()
Verse.TickManager:TickManagerUpdate ()
Verse.Game:UpdatePlay ()
Verse.Root_Play:Update ()

[Dubwise56]

only thing that could be null is the pawns joy need, does the pawn have a joy need or is it a weird modded alien thing?

[Georodin]

Im only playing with vanilla races, sometimes they swim but in 1 out of 5 cases I get this StackTrace
maybe should I provide something else as log the next time it occurs ?

[Dubwise56]

is the pool walled in on all sides?

[Georodin]

no but fancy tiles beneath it ^^ and around