fem::FiniteElement and fem::FunctionSpace are in a bit of a mess with respect to block size, value_shape and mixed elements. It's all a bit muddled. This is a first step of several to straighten things out. This change makes fem::FiniteElement::_reference_value_shape optional - it takes on a value only when it makes sense and when needed, i.e. not for mixed elements.
fem::FiniteElementandfem::FunctionSpaceare in a bit of a mess with respect to block size, value_shape and mixed elements. It's all a bit muddled. This is a first step of several to straighten things out. This change makesfem::FiniteElement::_reference_value_shapeoptional - it takes on a value only when it makes sense and when needed, i.e. not for mixed elements.