JavaScriptParser.ParseProgram throws on empty file with comments and Loc = true

[sam-lord]

// Copyright 2009 the Sputnik authors.  All rights reserved.
/**
 * Correct interpretation of single line comments
 *
 * @path ch07/7.4/S7.4_A1_T2.js
 * @description Simple test, create empty comment: ///
 */

//CHECK#1
///

Parsing the above file with this parser:

var parser = new JavaScriptParser(source, new ParserOptions
{
    Loc = true
});

Throws this exception:

System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.

Because a Location was initialised with start and end equal to (12, 0).

I believe the solution to this is modifying the Location constructor to allow the end to be equal to the start (but not precede it). I'll create a PR to reflect that, but I'd appreciate it if anyone can comment on whether the correct behaviour would be that start and end would equal (0, 0).