Remove blocks that are outside of loaded chunks from bitset list

Remove another potential source of unneeded calculations, if a digital
miner is chunkloaded and chunks it is considering are outside of loaded
chunks, they will be iterated through for each block mined.

common/mekanism/common/tile/TileEntityDigitalMiner.java

@@ -167,6 +167,7 @@ public class TileEntityDigitalMiner extends TileEntityElectricBlock implements I
 						
 						if(!coord.exists(worldObj))
 						{
+							toRemove.add(index);
 							next = index + 1;
 							continue;
 						}