Bind an entity reference instead of an rvalue

Summary

Whenever a local-function is bound to an element, the element should be passed as an lvalue and not an rvalue. The bind(Element const&) function takes just a const& so we don't know what we get. This MR, fixes the binding in the intersections and stores the bound element in some local-functions instead of just creating a pointer to the argument.

dune/curvedgrid/gridfunctions/discretegridviewfunction.hh

@@ -126,7 +126,8 @@ private:
     /// \brief vector that can be accessed in the operator() for interpolation
     void bind (const LocalContext& element)
     {
-      localView_.bind(element);
+      localContext_.emplace(element);
+      localView_.bind(*localContext_);
 
       const auto& leafNode = localView_.tree().child(0);
       localCoords_.resize(leafNode.size());
@@ -223,6 +224,7 @@ private:
     const VectorType& coords_;
 
     std::vector<RangeType> localCoords_;
+    std::optional<LocalContext> localContext_;
     std::optional<Geometry> geometry_;
     mutable std::vector<typename LocalBasis::Traits::RangeType> shapeValues_;
     mutable std::vector<typename LocalBasis::Traits::JacobianType> shapeGradients_;