Fixed missing virtual function

[abraverm]

@ph4m, I've adjusted your origianl PR (avin2#5) for this repository, with all credits to you. Let me know if this is a problem.
PointCloud Library maintainers, this PR fixes the following error, when running Platform/Linux/CreateRedist/RedistMaker:

In file included from /usr/include/ni/XnTypes.h:28:0, from /usr/include/ni/XnModuleInterface.h:27, from /usr/include/ni/XnModuleCppInterface.h:33, from ../../../../Source/XnDeviceSensorV2/XnSensorProductionNode.h:28, from ../../../../Source/XnDeviceSensorV2/XnSensorGenerator.h:28, from ../../../../Source/XnDeviceSensorV2/XnSensorMapGenerator.h:28, from ../../../../Source/XnDeviceSensorV2/XnSensorDepthGenerator.h:28, from ../../../../Source/XnDeviceSensorV2/XnSensorDepthGenerator.cpp:25: ../../../../Source/XnDeviceSensorV2/XnSensorDepthGenerator.cpp: In member function ‘virtual XnSensorGenerator* XnExportedSensorDepthGenerator::CreateGenerator(xn::Context&, xn::Device&, XnDeviceBase*, const XnChar*)’: /usr/include/ni/XnOS.h:331:49: error: invalid new-expression of abstract class type ‘XnSensorDepthGenerator’ #define XN_NEW(type, ...) new type(__VA_ARGS__) ^

[ph4m]

No problem on my side, happy you found that useful!

[taketwo]

I'm not even sure what is the status of this repository and how it is used. I guess @jspricke is the one who has to decide and merge.

[jspricke]

Which OpenNI version produces this error? Maybe you want the https://github.com/PointCloudLibrary/Sensor/tree/unstable branch?

[abraverm]

I have OpenNI installed from Fedora 25 repositories, version 1.5.7.10-8.fc25.
I was able to run Platform/Linux/CreateRedist/RedistMaker without errors from the unstable branch, however that version wasn't able to detect the Kinect (v1).