Hello, I am running hector_quadrotor_demo with "indoor_slam_gazebo.launch" launch file according to this tutorial http://www.ros.org/wiki/hector_quadrotor/Tutorials/Quadrotor%20indoor%20SLAM%20demo, it gives the following error:

*gazebo: /tmp/buildd/ros-electric-visualization-common-1.6.3/debian/ros-electric-visualization-common/opt/ros/electric/stacks/visualization_common/ogre/build/ogre_src_v1-7-3/OgreMain/include/OgreAxisAlignedBox.h:252: void Ogre::AxisAlignedBox::setExtents(const Ogre::Vector3&, const Ogre::Vector3&): Assertion `(min.x <= max.x && min.y <= max.y && min.z <= max.z) && "The minimum corner of the box must be less than or equal to maximum corner"' failed. ================================================================================REQUIRED process [gazebo-2] has died! process has died [pid 12268, exit code -6]. log files: /home/ling/.ros/log/a7ab0718-da89-11e1-8923-f04da2adc6ca/gazebo-2.log

Initiating shutdown!

[hector_geotiff_node-8] killing on exit [hector_trajectory_server-7] killing on exit [hector_mapping-6] killing on exit [ground_truth_to_tf-5] killing on exit [robot_state_publisher-4] killing on exit [spawn_robot-3] killing on exit [gazebo-2] killing on exit Traceback (most recent call last): File "/opt/ros/electric/stacks/simulator_gazebo/gazebo/scripts/spawn_model", line 330, in <module> sm.callSpawnService() File "/opt/ros/electric/stacks/simulator_gazebo/gazebo/scripts/spawn_model", line 237, in callSpawnService rospy.wait_for_service('/gazebo/get_physics_properties') File "/opt/ros/electric/stacks/ros_comm/clients/rospy/src/rospy/impl/tcpros_service.py", line 156, in wait_for_service raise ROSInterruptException("rospy shutdown") rospy.exceptions.ROSInterruptException: rospy shutdown [rosout-1] killing on exit [master] killing on exit shutting down processing monitor... ... shutting down processing monitor complete done**

Can any one tell why? And how to solve this problem?