In the middle of filtering the pairs to draw for the visualization

src/parse.cpp

@@ -357,7 +357,7 @@ namespace Parser {
                 ++(*index_in_text);
                 break;
             } else {
-                try head->value.pair.rest = Memory::create_lisp_object_pair(nullptr, nullptr);
+                try head->value.pair.rest = Memory::create_lisp_object_pair(Memory::nil, Memory::nil);
                 head = head->value.pair.rest;
             }
         }