本人使用的是Ubuntu14.04+indigo版本，在调试kinect V1摄像头时，使用命令“roslaunch openni_launch openni.launch”出现" Skipping XML Document "/opt/ros/indigo/share/gmapping/nodelet_plugins.xml" which had no Root Element. This likely means the XML is malformed or missing."这种情况，之后按照出错的路径：
/opt/ros/indigo/share/gampping，修改pacjage.xml文件，
删除：
<export>
<nodelet plugin="${prefix}/nodelet_plugins.xml" /></export>
即可。