[Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803

--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> ---
Another issue is that views::zip_transform returns
views::empty<decay_t<invoke_result_t<_Fp>>> when N == 0, which is not strictly
true, the standard requires that the return is the result of the *lvalue* F
being invoked, that is, views::empty<decay_t<invoke_result_t<decay_t<_Fp>&>>>.