PR2 crashes due to missing CameraSensor

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I'm trying to simulate the PR2 on Gazebo 1.9 and Groovy. When I launch gazebo using the pr2_description urdf, it crashes. Right before it crashes, it spits out errors like:

Error [SDF.cc:788] Missing element description for [depthImageTopicName]
Error [SDF.cc:788] Missing element description for [depthImageCameraInfoTopicName]
Error [CameraPlugin.cc:46] CameraPlugin requires a CameraSensor

I don't actually need the cameras at all, but I don't want to fiddle with the URDF in the pr2_description file. How do I fix this?