message: Update demo_turtlebot_mapping.launch
  Set "map_negative_poses_ignored" to avoid false obstacles when there is no scan reading (bug that will be fixed when devel will be merged).
diff: <node name="rtabmap" pkg="rtabmap_ros" type="rtabmap" output="screen" args="$(arg args)">
  <param name="database_path" type="string" value="$(arg database_path)"/>
  <param name="frame_id" type="string" value="base_footprint"/>
  - <param name="odom_frame_id" type="string" value="odom"/>
  <param name="wait_for_transform_duration" type="double" value="$(arg wait_for_transform)"/>
  <param name="subscribe_depth" type="bool" value="true"/>
  <param name="subscribe_scan" type="bool" value="true"/>
  + <param name="map_negative_poses_ignored" type="bool" value="true"/>
  <!-- inputs -->
  <remap from="scan" to="/scan"/>
  <remap from="rgb/image" to="$(arg rgb_topic)"/>
  <remap from="depth/image" to="$(arg depth_topic)"/>
  <remap from="rgb/camera_info" to="$(arg camera_info_topic)"/>
  + <remap unless="$(arg rgbd_odometry)" from="odom" to="/odom"/>
  <!-- output -->
  <remap from="grid_map" to="/map"/>
  