Broken json_cast in current origin/master

[repeatedly]

I have following code:

#include <pficommon/text/json.h>
#include <string>
#include <vector>

using namespace std;
using namespace pfi::text::json;

int main()
{
  json hoge(new json_object());
  vector<string> strs(json_cast<vector<string> >(hoge));

  return 0;
}

Current origin/master works.
But old version(e.g. pficommon 1.3.1) raises json_bad_cast.

$ ./a.out
terminate called after throwing an instance of 'pfi::text::json::json_bad_cast<std::vector<std::string, std::allocator<std::string> > >'
  what():  Failed json_cast from N3pfi4text4json11json_objectE to St6vectorISsSaISsEE.
zsh: abort      ./a.out

Older behavior seems to be correct.
"{}" should not be converted to vector, it's a map.

P.S.

d0d7361

This commit introduces new behavior.