Program: 21822
Project: 21822
Buggy source:
private static void explosionReaction(World world,Entity entity,int x,int y,int z,ChemicalFluidReactionRule rule,boolean popFlowingFluid){
  ChemicalFluidReactionOutput output=reactionRules.get(rule);
  if (output == null) {
    return;
  }
  if (output.explosionLevel != Float.NaN) {
    world.createExplosion(null,x,y,z,output.explosionLevel,true);
  }
  int foundVectors=0;
  Vector[] availableSpaces=new Vector[3];
  for (int i=0; i < availableSpaces.length; i++) {
    availableSpaces[i]=findAvailableSpacesAtCrossSection(world,x,y - 1 + i,z,1);
    foundVectors+=availableSpaces[i].size();
  }
  int needVectors=output.outputs.size();
  Iterator<MinechemChemicalType> it=output.outputs.keySet().iterator();
  while (it.hasNext() && needVectors > 0 && foundVectors > 0) {
    MinechemChemicalType chemical=it.next();
    boolean isGas=chemical.roomState().isGas();
    if (ran.nextFloat() <= output.outputs.get(chemical)) {
      Vector3 vector=null;
      if (isGas) {
        for (int i=availableSpaces.length - 1; i > -1; i--) {
          if (!availableSpaces[i].isEmpty()) {
            vector=(Vector3)availableSpaces[i].remove(availableSpaces[i].size() - 1);
            break;
          }
        }
      }
 else {
        for (int i=0; i < availableSpaces.length; i++) {
          if (!availableSpaces[i].isEmpty()) {
            vector=(Vector3)availableSpaces[i].remove(availableSpaces[i].size() - 1);
            break;
          }
        }
      }
      if (vector == null) {
        ItemStack itemStack=MinechemUtil.createItemStack(chemical,1);
        MinechemUtil.throwItemStack(world,itemStack,x,y,z);
      }
 else {
        int px=vector.intX();
        int py=vector.intY();
        int pz=vector.intZ();
        world.func_147480_a(px,py,pz,true);
        world.setBlockToAir(px,py,pz);
        Block fluidBlock=null;
        if (chemical instanceof ElementEnum) {
          fluidBlock=FluidHelper.elementsBlocks.get(FluidHelper.elements.get(chemical));
        }
 else         if (chemical instanceof MoleculeEnum) {
          fluidBlock=FluidHelper.moleculeBlocks.get(FluidHelper.molecule.get(chemical));
        }
        if (fluidBlock != null) {
          world.setBlock(px,py,pz,fluidBlock,popFlowingFluid ? 1 : 0,3);
        }
      }
    }
  }
}

Fixed version (ground truth):
private static void explosionReaction(World world,Entity entity,int x,int y,int z,ChemicalFluidReactionRule rule,boolean popFlowingFluid){
  ChemicalFluidReactionOutput output=reactionRules.get(rule);
  if (output == null) {
    return;
  }
  if (output.explosionLevel != Float.NaN) {
    world.createExplosion(null,x,y,z,output.explosionLevel,true);
  }
  int foundSpaces=0;
  int halfSpace=FLUIDS_GENERATE_SPACE / 2;
  List[] availableSpaces=new List[FLUIDS_GENERATE_SPACE];
  for (int i=0; i < availableSpaces.length; i++) {
    availableSpaces[i]=findAvailableSpacesAtCrossSection(world,x,y - halfSpace + i,z,1);
    foundSpaces+=availableSpaces[i].size();
  }
  int needSpaces=output.outputs.size();
  Iterator<MinechemChemicalType> it=output.outputs.iterator();
  while (it.hasNext() && needSpaces > 0 && foundSpaces > 0) {
    MinechemChemicalType chemical=it.next();
    boolean isGas=chemical.roomState().isGas();
    CoordTuple coords=null;
    if (isGas) {
      for (int i=availableSpaces.length - 1; i > -1; i--) {
        if (!availableSpaces[i].isEmpty()) {
          coords=(CoordTuple)availableSpaces[i].remove(availableSpaces[i].size() - 1);
          break;
        }
      }
    }
 else {
      for (int i=0; i < availableSpaces.length; i++) {
        if (!availableSpaces[i].isEmpty()) {
          coords=(CoordTuple)availableSpaces[i].remove(availableSpaces[i].size() - 1);
          break;
        }
      }
    }
    if (coords == null) {
      ItemStack itemStack=MinechemUtil.createItemStack(chemical,1);
      MinechemUtil.throwItemStack(world,itemStack,x,y,z);
    }
 else {
      int px=coords.getX();
      int py=coords.getY();
      int pz=coords.getZ();
      world.func_147480_a(px,py,pz,true);
      world.setBlockToAir(px,py,pz);
      Block fluidBlock=null;
      if (chemical instanceof ElementEnum) {
        fluidBlock=FluidHelper.elementsBlocks.get(FluidHelper.elements.get(chemical));
      }
 else       if (chemical instanceof MoleculeEnum) {
        fluidBlock=FluidHelper.moleculeBlocks.get(FluidHelper.molecule.get(chemical));
      }
      if (fluidBlock != null) {
        world.setBlock(px,py,pz,fluidBlock,popFlowingFluid ? 1 : 0,3);
      }
    }
  }
}