This error comes from the Quantum Espresso routine dos.x that calculates DOS, so it has nothing to do with DOS plotting in the VNL as such. I see nothing obviously wrong in the QE input file for DOS calculation. You may try to adjust the Al dos input file (which works as you say) for halite. Maybe your text editor has added something hidden in the halite_dos.in file, i.e., there might be something wrong with text formatting, and the dos.x is reading something it is not supposed to be in the dos input file. This is just my guess.