FIX: Transaction::GetResultSet() now always returns a good reference

CHANGELOG.md

@@ -20,4 +20,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* #11 - Transaction::GetResultSet() now always returns a valid reference.
+
 ### Security

include/caosdb/transaction.h

@@ -365,6 +365,10 @@ public:
   [[nodiscard]] inline auto GetStatus() const noexcept -> TransactionStatus { return this->status; }
 
   [[nodiscard]] inline auto GetResultSet() const noexcept -> const ResultSet & {
+    if (!this->result_set) {
+      this->result_set = std::make_unique<MultiResultSet>(
+          std::move(std::vector<std::unique_ptr<Entity>>()));
+    }
     return *(this->result_set.get());
   }