Getting this exception every time I try to force any interaction (any worktable, item, farming zone)

Root level exception in OnGUI(): System.NullReferenceException: Object reference not set to an instance of an object
at Advanced_Cultivation.WorkGiver_Till/<PotentialWorkCellsGlobal>d__4.MoveNext () <0x0038e>
at System.Linq.Enumerable.Contains<Verse.IntVec3> (System.Collections.Generic.IEnumerable`1<Verse.IntVec3>,Verse.IntVec3,System.Collections.Generic.IEqualityComparer`1<Verse.IntVec3>) <0x00106>
at System.Linq.Enumerable.Contains<Verse.IntVec3> (System.Collections.Generic.IEnumerable`1<Verse.IntVec3>,Verse.IntVec3) <0x00108>
at RimWorld.FloatMenuMakerMap.AddJobGiverWorkOrders (Verse.IntVec3,Verse.Pawn,System.Collections.Generic.List`1<Verse.FloatMenuOption>,bool) <0x018c5>
at RimWorld.FloatMenuMakerMap.AddUndraftedOrders (UnityEngine.Vector3,Verse.Pawn,System.Collections.Generic.List`1<Verse.FloatMenuOption>) <0x0036d>
at RimWorld.FloatMenuMakerMap.ChoicesAtFor (UnityEngine.Vector3,Verse.Pawn) <0x00324>
at RimWorld.FloatMenuMakerMap.TryMakeFloatMenu (Verse.Pawn) <0x0019f>
at (wrapper dynamic-method) RimWorld.Selector.HandleMapClicks_Patch1 (object) <0x002a4>
at RimWorld.Selector.SelectorOnGUI () <0x0001c>
at RimWorld.MapInterface.HandleLowPriorityInput () <0x0006d>
at RimWorld.UIRoot_Play.UIRootOnGUI () <0x002f9>
at Verse.Root.OnGUI () <0x00112>

Verse.Log:Error(String, Boolean)
Verse.Root:OnGUI()

Apparently it's some incompatibility. Trying to figure out which mod messes things up.
Edit: Or maybe it requires a new save, 'cause haven't had this problem after starting a new game with same mods.

My citizens keep tilling the same tile over and over again. The progress bar completes, the tile changes to tilled but the worker starts tilling it again.
Log says:
Tried to set terrain at (113, 0, 107) to null.
Verse.Log:Error(String, Boolean)
Verse.TerrainGrid:SetTerrain(IntVec3, TerrainDef)
Advanced_Cultivation.<>c__DisplayClass4_0:<MakeNewToils>b__1()
Verse.AI.JobDriver:DriverTick_Patch1(Object)
Verse.AI.Pawn_JobTracker:JobTrackerTick()
Verse.Pawn:Tick_Patch1(Object)
Verse.TickList:Tick()
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update()

@SheakZarnn Do you have mods which alter terrain? This mod should be save game compatible.

@johnny Do you have mods which alter terrain? What terrain are they tilling repeatedly?

I am using a lot of mods, though afaik none of them alters terrains. The repeated tilling happens on any kind of tiles, at least on soil and rich soil. When I force someone to do the tilling, he usually starts with the assigned tile, then changes once to a different adjacent tile and continues forever on that tile until it is time to go to sleep (eat, ...)
I'll try disabling a few other mods (among others, theres some that change working priorities etc.) to narrow down the problem ...

Ok, after some testing I found the culprit:
Local Growing First (1433579722)
You could add that mod as an incompatibility ... seems logical now that I realised it ;)
Sorry to bother you about it!

@johnny Please, PLEASE bother me about incompatibilities and bugs. The worst thing you could do when you encounter a bug is unsub and never use my mod. I want to fix bugs and incompatibilities. Thank you for the report! I'll take a look at that mod and see if I can resolve it. We likely both alter toils given by jobdrivers and there's some clash.

EDIT: After quickly looking at the code for Local Growing First, it looks like that mod does not use harmony! I don't think I can fix this without rewriting that mod. That mod is likely to conflict with anything that alters growing jobs.

@Gasch, yes I do, and that broke the save, no big deal for me (already started a new game), and as I said, everything runs smoothly.
I get the same error johnny mentioned, when pawn harvests/chops down a wild plant growing on rich soil, but haven't checked if that's mod incompatibility or internal bug. Probably will run a clean game later today and will tell you the results.

@SheakZarnn sorry for the broken save! As for the new message... that's likely an internal bug and I think I know the fix. I'll be home in a few hours and test and push it asap.

@Gasch, so, I found out that it only happens if I use 'chop wood' or 'harvest' command from the architect menu. Harvesting plants individually (selecting a plant and clicking harvest/chop command) proceeds without errors.

Also, I think you need to look into tilling mechanics. Pawns till soil even without corresponding research. The option to till soil doesn't even appear in the command menu, but they do it anyways.

Now I also tried to change the time needed for tilling and found out that your suggestion does not work anymore. Instead, I added values for <tillWorkAmount>X</tillWorkAmount> in Vanilla_Overwrites_AC.xml. Maybe you could create a mod option to configure this - as it is probably dependent on the overall difficulty of the mod combination used, e.g. in my case it would take months to till the fields necessary for food for one year ...

@johnny yeah, mod options is something I've been meaning to look into for some time.

As of the current release (V1.1.2), many bugs have been squashed.

I am running into an odd problem. Both of the fertilizers that are crafted at the drug bench cant seem to be crafted. I have them researched, tons of supplies, high skill colonist, but I cannot seem to get them to craft it. There isnt even a force option.

@Dess if your pawns can't interact with drug lab, then it's most likely another mod (that changes drug lab properties) incompatibility. Enable dev mode and check if there're any exceptions or errors (displayed in red text) when you load the save, and when you try to force an interaction with a drug lab