two consecutive spaces removed from strings

I think this time it's a genuine bug:

$ cat t.js 
class A {
	a() {
    var spaces = '  ';
    var a = '1 2  3   4    5     6      end';
  }
}
$ ./bin/buble t.js 
var A = function A () {};

A.prototype.a = function a () {
  var spaces = '';
  var a = '1 23 4  5   6    end';
};