PointIndexLeafNode is missing at least one constructor. Trying to use the new Grid::apply() dispatch method is resulting in this error:

no matching function for call to 'openvdb::v6_0::tools::PointIndexLeafNode<openvdb::v6_0::PointIndex<unsigned int, 0u>, 3u>::PointIndexLeafNode(openvdb::v6_0::tools::PointIndexLeafNode<openvdb::v6_0::PointIndex<unsigned int, 0u>, 3u>&, const ValueType&, openvdb::v6_0::TopologyCopy)`

I suggest we extend TestGrid::testApply() to test dispatch of all grid types and fix the issues with the PointIndexGrid.

pcucka - is this something you could take a look at?