Fix memory leak in graph manager (#147) (#148)

Signed-off-by: Pablo Garrido <pablogs9@gmail.com>
(cherry picked from commit c89776e1fd)

Co-authored-by: Pablo Garrido <pablogs9@gmail.com>

micro_ros_agent/include/agent/graph_manager/graph_manager.hpp

@@ -111,6 +111,12 @@ public:
         const eprosima::fastdds::dds::DomainParticipant* participant,
         bool from_microros = true);
 
+    /**
+     * @brief   Getter for the graph cache.
+     * @return  Reference to inner graph cache
+     */
+    rmw_dds_common::GraphCache& get_graph_cache() { return graphCache_; }
+
     /**
      * @brief   Adds a DDS datawriter to the graph tree.
      * @param   datawriter_guid rtps::GUID_t of the datawriter to be added.