If you find yourself needing to make a blank .chr file for an NES homebrew game, here is a quick shell script to create a blank 8 KB .chr file.

#! /bin/bash
for ((a=0; a <= 8191 ; a++))
do
    printf "\x00" >> file_name.chr
done

It just writes out 8,192 bytes of zeros into a binary file. You should then be able to open this up in a .chr editor.