The "get_data" function no longer converts charset and data parameters to "" if either is undefined.

1) The "get_data" function no longer converts charset and data parameters to "" if either is undefined. This was causing "GET" data requests in with undefined data parameters to append "?" at the end of the request.

2) The "make_request" function has been slightly re-structured and modified to prevent "?" from being appended if the request method is "GET" and the data string is undefined, or is null, or is an empty string.