When reading, don't add items to a vector before they are read. This avoids nullptrs in the list of fields, cards, etc. when exceptions are thrown

src/util/io/reader.hpp

@@ -217,9 +217,10 @@ template <typename T>
 void Reader::handle(const Char* name, vector<T>& vector) {
   String vectorKey = singular_form(name);
   while (enterBlock(vectorKey.c_str())) {
-    vector.resize(vector.size() + 1);
+    T item;
-    handle_greedy(vector.back());
+    handle_greedy(item);
-    update_index(vector.back(), vector.size() - 1); // update index for IndexMap
+    update_index(item, vector.size()); // update index for IndexMap
+    vector.emplace_back(std::move(item));
     exitBlock();
   }
 }