message: null pwd support
diff: @@ -524,6 +524,8 @@ static int mysql_handshake(mysql_connector *connector, char *buf, int len)
  tmp[connector->user_len] = '\0';
  tmp += (connector->user_len + 1);
  + if (connector->password_len > 0)
  + {
  //auth-response
  char hash_0[20];
  bzero(hash_0, sizeof (hash_0));
  @@ -555,6 +557,12 @@ static int mysql_handshake(mysql_connector *connector, char *buf, int len)
  *tmp = 20;
  memcpy(tmp + 1, hash_3, 20);
  tmp += 21;
  + }
  + else
  + {
  + *tmp = 0;
  + tmp++;
  + }
  //string[NUL] database
  memcpy(tmp, connector->database, connector->database_len);
  