Conditional deserialization of message for ros2 topic hz (#1005)

Signed-off-by: Kostubh Khandelwal <[email protected]>

Author: exMachina316

ros2topic/ros2topic/verb/hz.py

@@ -316,7 +316,8 @@ def _rostopic_hz(node, topics, qos_args, window_size=DEFAULT_WINDOW_SIZE, filter
             msg_class,
             topic,
             functools.partial(rt.callback_hz, topic=topic),
-            qos_profile)
+            qos_profile,
+            raw=filter_expr is None)
         if topics_len > 1:
             print('Subscribed to [%s]' % topic)