A detailed walkthrough of the error, its code path and all known details is as follows:
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-- Head --
Stacktrace:
	at extrautils.tileentity.transfernodes.nodebuffer.ItemBuffer.transfer(ItemBuffer.java:49)
	at extrautils.tileentity.transfernodes.pipes.PipeBase.transferItems(PipeBase.java:42)
	at extrautils.tileentity.transfernodes.TileEntityTransferNode.transferItems(TileEntityTransferNode.java:370)
	at extrautils.tileentity.transfernodes.TileEntityTransferNode.handleInventories(TileEntityTransferNode.java:246)
	at extrautils.tileentity.transfernodes.TileEntityTransferNodeInventory.func_70316_g(TileEntityTransferNodeInventory.java:83)

-- Tile entity being ticked --
Details:
	Name: transferNode // extrautils.tileentity.transfernodes.TileEntityTransferNodeInventory
	Block type: ID #2513 (tile.extrautils:extractor_base // extrautils.tileentity.transfernodes.BlockTransferNode)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (9515,59,-15963), Chunk: (at 11,3,5 in 594,-998; contains blocks 9504,0,-15968 to 9519,255,-15953), Region: (18,-32; contains chunks 576,-1024 to 607,-993, blocks 9216,0,-16384 to 9727,255,-15873)
	Actual block type: ID #2513 (tile.extrautils:extractor_base // extrautils.tileentity.transfernodes.BlockTransferNode)
	Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
	at net.minecraft.world.World.func_72939_s(World.java:2752)