0.24.0 xt::linalg::pinv build issue introduced

[tatatupi]

After updating my xtensor version from 0.23.10 to 0.24.0, my project has run into a buildtime error for xt::linalg::pinv usage. I tried using pinv for a xarray<float> and for xtensor<float, 2> and the problem was the same.

It seems something is wrong with xassign, and I guess it might have been introduced in PR #2393.

Parts of the error message:

xassign.hpp:582: Expressions of type void cannot be converted to other types
xassign.hpp(582): error C2440: '=': cannot convert from 'void' to '_Ty

xutils.hpp:677: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
xutils.hpp(692): note: see reference to function template instantiation 'auto xt::conditional_cast_functor<true,T>::operator ()<_Ty>(U &&) const' being compiled

After downgrading it back to 0.23.10, everything worked fine.