Error 02 020617

Dean threw exception in WorkGiver ConstructFinishFrames: System.NullReferenceException: Object reference not set to an instance of an object
  at RimWorld.Frame.MaterialsNeeded () [0x00000] in <filename unknown>:0
  at RimWorld.WorkGiver_ConstructFinishFrames.JobOnThing (Verse.Pawn pawn, Verse.Thing t) [0x00000] in <filename unknown>:0
  at RimWorld.WorkGiver_Scanner.HasJobOnThing (Verse.Pawn pawn, Verse.Thing t) [0x00000] in <filename unknown>:0
  at RimWorld.JobGiver_Work+<TryGiveJob>c__AnonStorey277.<>m__141 (Verse.Thing t) [0x00000] in <filename unknown>:0
  at Verse.GenClosest+<ClosestThingReachable>c__AnonStorey532.<>m__9FC (Verse.Thing t) [0x00000] in <filename unknown>:0
  at Verse.GenClosest.ClosestThing_Global (IntVec3 center, IEnumerable searchSet, Single maxDistance, System.Predicate`1 validator) [0x00000] in <filename unknown>:0
  at Verse.GenClosest.ClosestThingReachable (IntVec3 root, Verse.Map map, ThingRequest thingReq, PathEndMode peMode, TraverseParms traverseParams, Single maxDistance, System.Predicate`1 validator, IEnumerable`1 customGlobalSearchSet, Int32 searchRegionsMax, Boolean forceGlobalSearch) [0x00000] in <filename unknown>:0
  at RimWorld.JobGiver_Work.TryGiveJob (Verse.Pawn pawn) [0x00000] in <filename unknown>:0
Verse.Log:Error(String)
RimWorld.JobGiver_Work:TryGiveJob(Pawn)
Verse.AI.ThinkNode_JobGiver:TryIssueJobPackage(Pawn)
Verse.AI.ThinkNode_PrioritySorter:TryIssueJobPackage(Pawn)
Verse.AI.ThinkNode_Subtree:TryIssueJobPackage(Pawn)
Verse.AI.ThinkNode_Priority:TryIssueJobPackage(Pawn)
RimWorld.ThinkNode_Conditional:TryIssueJobPackage(Pawn)
Verse.AI.ThinkNode_Priority:TryIssueJobPackage(Pawn)
Verse.AI.Pawn_JobTracker:DetermineNextJob(ThinkTreeDef&)
Verse.AI.Pawn_JobTracker:TryFindAndStartJob()
Verse.AI.Pawn_JobTracker:EndCurrentJob(JobCondition, Boolean)
Verse.AI.Pawn_JobTracker:JobTrackerTick()
Verse.Pawn:Tick()
Verse.TickList:Tick()
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:Update()
Verse.Root_Play:Update()