adapt RootGM::TessellatedSolid for ROOT 6.32.00

Bug: https://github.com/vmc-project/vgm/pull/16
---
 packages/RootGM/source/solids/TessellatedSolid.cxx | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/packages/RootGM/source/solids/TessellatedSolid.cxx
+++ b/packages/RootGM/source/solids/TessellatedSolid.cxx
@@ -178,13 +178,16 @@ VGM::ThreeVector RootGM::TessellatedSolid::Vertex(int ifacet, int index) const
 {
   CheckVertexIndex(ifacet, index);
 
-  const TGeoFacet& facet = fTessellated->GetFacet(ifacet);
+#if ROOT_VERSION_CODE > ROOT_VERSION(6, 30, 4)
+  const auto& rvertex =  fTessellated->GetVertex((fTessellated->GetFacet(ifacet))[index]);
+#else
+  const auto& rvertex =  fTessellated->GetFacet(ifacet).GetVertex(index);
+#endif
 
   VGM::ThreeVector vertex;
-  vertex.push_back(facet.GetVertex(index).fVec[0] * RootGM::Units::Length());
-  vertex.push_back(facet.GetVertex(index).fVec[1] * RootGM::Units::Length());
-  vertex.push_back(facet.GetVertex(index).fVec[2] * RootGM::Units::Length());
+  vertex.push_back(rvertex.fVec[0] * RootGM::Units::Length());
+  vertex.push_back(rvertex.fVec[1] * RootGM::Units::Length());
+  vertex.push_back(rvertex.fVec[2] * RootGM::Units::Length());
 
   return vertex;
 }
-