refuse to escape strings with null bytes (#425)

PHP also refuse to escape strings with null bytes, using a similar message. (not to mention, it's *literally impossible* to escape null bytes)

src/php/exec/escapeshellarg.js

@@ -8,6 +8,10 @@ module.exports = function escapeshellarg (arg) {
  // example 2: escapeshellarg("/home'; whoami;''")
  // returns 2: "'/home'\''; whoami;'\'''\'''"
 
+ if(arg.indexOf("\x00") !== -1) {
+ throw new Error('escapeshellarg(): Argument #1 ($arg) must not contain any null bytes');
+ }
+
  var ret = ''
 
  ret = arg.replace(/\'/g, '\'\\\'\'')