Run openni_tracker with a simulated kinect using Gazebo

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Hi everybody, we use gazebo to simulate the kinect sensor. is there any option to run the openni_tracker package without using the real sensor? when we try to run it: roslaunch openni_launch openni.launch load_driver:=false depth_registration:=true camera:=camera rosrun openni_tracker openni_tracker we have got the following error: InitFromXml failed: Can't create any node of the requested type!

thank you all in advance