Fix VTK compatibility

https://github.com/fran6co/pcl/commit/4d1ee479e8fc791b5a7b0f75ecb109105bbe6d48#diff-4206b5bbfa76680243fec88c91dfbd3cL119 removed the update call which is in fact needed for VTK 5. It does not hurt VTK 6 support.

Reported by Ber461 on the [mailing list](http://www.pcl-users.org/Segmentation-fault-on-trunk-version-of-pcl-apps-RenderViewsTesselatedSphere-td4036447.html).