[Core] DrawMesh<Hexahedron>: add quick test for quads when drawing hexa (#6152)

* add quick test for quads when drawing hexa

* add tests for triangles/tetra too

Author: fredroy

Sofa/framework/Core/src/sofa/core/visual/DrawMesh.h

@@ -328,6 +328,17 @@ struct SOFA_CORE_API DrawElementMesh<sofa::geometry::Tetrahedron>
         const auto& elements = topology->getTetrahedra();
         const auto& facets = topology->getTriangles();
 
+        if(facets.empty())
+        {
+            static bool firstTime = true;
+            if (firstTime)
+            {
+                msg_error("DrawElementMesh<Tetrahedron>") << "Drawing tetrahedra needs the associated triangles in the topology.";
+                firstTime = false;
+            }
+            return;
+        }
+
         for ( auto& p : renderedPoints)
         {
             p.resize(elementIndices.size() * sofa::geometry::Triangle::NumberOfNodes);
@@ -474,6 +485,17 @@ struct SOFA_CORE_API DrawElementMesh<sofa::geometry::Hexahedron>
         const auto& elements = topology->getHexahedra();
         const auto& facets = topology->getQuads();
 
+        if(facets.empty())
+        {
+            static bool firstTime = true;
+            if (firstTime)
+            {
+                msg_error("DrawElementMesh<Hexahedron>") << "Drawing hexahedra needs the associated quads in the topology.";
+                firstTime = false;
+            }
+            return;
+        }
+
         for ( auto& p : renderedPoints)
         {
             p.resize(elementIndices.size() * sofa::geometry::Quad::NumberOfNodes);