bug#45333: complex command history should not save optional nil parameters

[Drew Adams]

> > (replace-string "foo" "bar" nil nil nil nil nil)
> >
> > in `command-history' -- where all those nils are optional.  We could
> > pretty easily filter those out by looking at the signature of the
> > function and peeling off trailing nils, I think?  Would there be any
> > disadvantages to doing so?
> 
> Note that there are only such `nil`s when the evaluation of the
> interactive spec returned them.  It's somewhat consistent if the
> command history includes the argument list exactly as returned by
> `interactive'...
> 
> Anyway, trying of prettify away those `nil`s seems like overkill to me.
> In theory even an optional `nil' can be significant.

+1.

Among other uses, `repeat-complex-command' shows
a user just what args were passed to the function.