Fix wrong-number-of-args error in Music_function::call

Fix wrong-number-of-args error in Music_function::call

When a music function called via Scheme wanted to report a bad argument
type, it instead triggered a Scheme error wrong-number-of-args because
of a spurious `location' argument.  This was an oversight in issue 4455
and was converted into equivalently bad code by several other issues
touching this code.