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Hi all,

I'm getting a NullPointerException due to a null parent in  
GPNode.parentType() when I use RandTree. I believe this is caused by  
line 416 in RandTree.java where the parent is set to null, but I'm not  
sure (I can verify that the argposition of the GPNode in question is 0  
in this case too). Stack trace is attached.

Exception in thread "main" java.lang.NullPointerException
	at ec.gp.GPNode.parentType(GPNode.java:219)
	at  
ec.gp.breed.MutateOneNodePipeline.produce(MutateOneNodePipeline.java: 
216)
	at ec.breed.MultiBreedingPipeline.produce(MultiBreedingPipeline.java: 
125)
	at ec.simple.SimpleBreeder.breedPopChunk(SimpleBreeder.java:182)
	at ec.simple.SimpleBreeder.breedPopulation(SimpleBreeder.java:119)
	at ec.simple.SimpleEvolutionState.evolve(SimpleEvolutionState.java:119)
	at ec.EvolutionState.run(EvolutionState.java:371)
	at ec.Evolve.main(Evolve.java:648)