Poco::JSON::Object stringify endless loop

endless loop in the following code:

``` cpp
#include <Poco/JSON/Object.h>
#include <iostream>

int main (int argv, char** argc)
{
        Poco::JSON::Object obj;
        obj.set("one","two");
        obj.stringify(std::cout,4);  //this works 
        obj.stringify(std::cout,1);  //this never returns
        std::cout << std::endl;
}
```
