function unTrackToken(address _addr, uint16 _position) onlyAdmin external {
    require(isTokenTracked[_addr]);
    require(trackedTokens[_position] == _addr);

    ERC20(_addr).transfer(_addr, ERC20(_addr).balanceOf(address(this)));
    trackedTokens[_position] = trackedTokens[trackedTokens.length-1];
    delete trackedTokens[trackedTokens.length-1];
    trackedTokens.length--;
  }