Query::ExpresionEval - Null.prop is now Null

Reviewers: teon.banek

Reviewed By: teon.banek

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D329

src/query/interpret/eval.hpp

@@ -96,6 +96,9 @@ class ExpressionEvaluator : public TreeVisitorBase {
   void PostVisit(PropertyLookup &property_lookup) override {
     auto expression_result = PopBack();
     switch (expression_result.type()) {
+      case TypedValue::Type::Null:
+        result_stack_.emplace_back(TypedValue::Null);
+        break;
       case TypedValue::Type::Vertex:
         result_stack_.emplace_back(
             expression_result.Value<VertexAccessor>().PropsAt(