[BUG] ChannelAccessor has no valid channel pointer with VectorGrid

[ZephirFXEC]

Environment

Operating System: Win 10
Version: VDB 12.0

Describe the bug

I'm building an nanovdb::IndexGrid from an openvdb::FloatGrid. It encodes voxel values as blind data that can be accessed with a
nanovdb::ChannelAccessor<float, nanovdb::ValueOnIndex>, there everythings works as it should.

But when using an openvdb::VectorGrid and the accessor nanovdb::ChannelAccessor<nanovdb::Vec3f, nanovdb::ValueOnIndex> the channel ptr is empty.

To Reproduce

using SrcGridT  = openvdb::FloatGrid; // replace by opevdb::VectorGrid 
using DstBuildT = nanovdb::ValueOnIndex;
using BufferT   = nanovdb::cuda::DeviceBuffer;

nanovdb::GridHandle<BufferT> idxHandle = nanovdb::tools::createNanoGrid<SrcGridT, DstBuildT, BufferT>(*floatGrid /* *vectorGrid */, 1u, false , false, 0);
idxHandle.deviceUpload(stream, false);

const auto* gpuGrid = idxHandle.deviceGrid<DstBuildT>();
launch_kernels(gpuGrid, toSample, stream);

Then a cuda kernel is launched to access the grid on the GPU.

__global__ void gpu_kernel(const nanovdb::NanoGrid<nanovdb::ValueOnIndex>* gpuGrid, const float* data) {
	const nanovdb::ChannelAccessor<float /* nanovdb::Vec3f */, nanovdb::ValueOnIndex> acc(*gpuGrid);

	if (!acc) {
		printf("Error: ChannelAccessor has no valid channel pointer! (null)\n");
		return;
	}

	const uint32_t idx000 = acc.idx(0, 0, 0);
	printf("Idx at Coord 0,0,0 : %u\n", idx000);
}

Additional context

I tried different configurations such as adding 3u channel with the VectorGrid and trying to access each component individually but it didn't work.