spadd would crash if given incorrect arguments (#424)
spadd would crash if given incorrect arguments (#424)

A combination of shift, 'new', and 'range' could give
incorrect results for spadd if the fn values were different
in curexp and addsubexp
OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ