DPL: properly handle getting non-existing bindinds

The current code only works because the template specialization happens
late enough.

This might or might not be the case, depending for example if one decides to
force a given table's code out-of-line.

Framework/Core/include/Framework/ASoA.h

@@ -781,6 +781,11 @@ struct ColumnDataHolder {
   arrow::ChunkedArray* second;
 };
 
+template <typename T, typename B>
+concept CanBind = requires(T&& t) {
+  { t.B::mColumnIterator };
+};
+
 template <typename IP, typename... C>
 struct RowViewCore : public IP, C... {
  public:
@@ -964,7 +969,27 @@ struct RowViewCore : public IP, C... {
   template <typename DC, typename... B>
   auto bindDynamicColumn(framework::pack<B...>)
   {
-    DC::boundIterators = std::make_tuple(&(B::mColumnIterator)...);
+    DC::boundIterators = std::make_tuple(getDynamicBinding<B>()...);
+  }
+
+  // Sometimes dynamic columns are defined for tables in
+  // the hope that it will be joined / extended with another one which provides
+  // the full set of bindings. This is to avoid a compilation
+  // error if constructor for the table or any other thing involving a missing
+  // binding is preinstanciated.
+  template <typename B>
+    requires(CanBind<typename table_t::iterator, B>)
+  decltype(auto) getDynamicBinding()
+  {
+    static_assert(std::is_same_v<decltype(&(static_cast<B*>(this)->mColumnIterator)), std::decay_t<decltype(B::mColumnIterator)>*>, "foo");
+    return &(static_cast<B*>(this)->mColumnIterator);
+    //return static_cast<std::decay_t<decltype(B::mColumnIterator)>*>(nullptr);
+  }
+
+  template <typename B>
+  decltype(auto) getDynamicBinding()
+  {
+    return static_cast<std::decay_t<decltype(B::mColumnIterator)>*>(nullptr);
   }
 };