[Mesh] fix the nonlinear node ID check

MeshLib/Mesh.cpp

@@ -42,7 +42,7 @@ Mesh::Mesh(const std::string &name,
     assert(n_base_nodes <= nodes.size());
     this->resetNodeIDs();
     this->resetElementIDs();
-    if (isNonlinear())
+    if ((n_base_nodes==0 && hasNonlinearElement()) || isNonlinear())
         this->checkNonlinearNodeIDs();
     this->setDimension();
     this->setElementsConnectedToNodes();
@@ -278,6 +278,17 @@ void Mesh::checkNonlinearNodeIDs() const
     }
 }
 
+bool Mesh::hasNonlinearElement() const
+{
+    for (auto* const e : _elements)
+    {
+        if (e->getNumberOfNodes() == e->getNumberOfBaseNodes())
+            continue;
+        return true;
+    }
+    return false;
+}
+
 void scaleMeshPropertyVector(MeshLib::Mesh & mesh,
                              std::string const& property_name,
                              double factor)

MeshLib/Mesh.h

@@ -165,6 +165,9 @@ protected:
     /// Check if all the nonlinear nodes are stored at the end of the node vector
     void checkNonlinearNodeIDs() const;
 
+    /// Check if the mesh contains any nonlinear element
+    bool hasNonlinearElement() const;
+
     std::size_t const _id;
     unsigned _mesh_dimension;
     /// The minimal and maximal edge length over all elements in the mesh