Attribute error in message filtering method

[lyletbjohnson]

At runtime the Novatel driver reports the following:

Exception in thread Thread-5:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/home/dev/ros_ws/src/novatel_span_driver/novatel_span_driver/src/novatel_span_driver/data.py", line 76, in run
    if header.id not in pkt_counters:
AttributeError: 'NoneType' object has no attribute 'id'

At the time the error occurred, the launch file parameters were set to the following:

  <group ns="$(arg novatel_frame_id)" if="$(arg with_novatel)">
    <node name="novatel_span_driver" pkg="novatel_span_driver" type="driver">
      <param name="ip" value="$(arg novatel_ip)" />
      <param name="port" value="$(arg novatel_port)" />
      <rosparam ns="configuration">
       log_request:
        inspvaxb: 0.02
        bestposb: 0.1
        corrimudatab: 0.02
        inscovb: 1
      </rosparam>


      <!-- Whether or not the driver should publish a TF, and what frames it should
         be between. This configuration publishes odom -> base_link.--> 
    <param name="publish_tf" value="false" />
    <param name="odom_frame" value="odom" />
    <param name="base_frame" value="base_link" />

    <!-- IMU rate; controls scaling of the imu/data topic values. This is a
         function of the underlying hardware IMU rate, which is 100Hz for IMU-CPT.--> 
    <param name="rate" value="330" />

    <!-- Disable this if you don't want SPAN to use wheel encoder data. Remap the odom
         topic if your encoders publish elsewhere. -->
    <param name="enable_wheel_velocity" value="false" />

    <!-- Disable this if you'd like the Odometry to be absolute within the UTM zone
         rather than starting from an arbitrary zero origin.--> 
    <param name="zero_start" value="true" />
  </node>
  </group>

The launch file has since been updated to request inspvax and corrimudata at <=20Hz, as recommended by the Novatel documentation.

I will continue updating this issue with information to help narrow down the root cause.