App crashes when I try to get the position attribute of a QMesh (Qt 5.15.2)

[franco.amato]

I try to get the position attribute of a mesh using the following code

....code...
   Qt3DRender::QMesh *mesh = new Qt3DRender::QMesh();
    mesh->setMeshName("mesh");
    // Import mesh data from a ply file (monster.ply located at same level of the executable)
    mesh->setSource(QUrl::fromLocalFile("monster.ply"));
 
    // The call to mesh->geometry() crashes my app
    if (mesh->primitiveType() == Qt3DRender::QGeometryRenderer::Triangles)
    {
        for(int i = 0; i < mesh->geometry()->attributes().size(); ++i)
        {
            // To have access to data
            mesh->geometry()->attributes().at(i)->buffer()->setSyncData(true);
        }
 
        // Now I need to get the position of the vertices of the triangles
 
        Qt3DRender::QAttribute *positionAttribute = mesh->geometry()->attributes().at(0);
        ...more code...
    }

....code...
   Qt3DRender::QMesh *mesh = new Qt3DRender::QMesh();
    mesh->setMeshName("mesh");
    // Import mesh data from a ply file (monster.ply located at same level of the executable)
    mesh->setSource(QUrl::fromLocalFile("monster.ply"));

    // The call to mesh->geometry() crashes my app
    if (mesh->primitiveType() == Qt3DRender::QGeometryRenderer::Triangles)
    {
        for(int i = 0; i < mesh->geometry()->attributes().size(); ++i)
        {
            // To have access to data
            mesh->geometry()->attributes().at(i)->buffer()->setSyncData(true);
        }

        // Now I need to get the position of the vertices of the triangles

        Qt3DRender::QAttribute *positionAttribute = mesh->geometry()->attributes().at(0);
        ...more code...
    }

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This is the content of the qmake script

QT += 3dcore 3drender 3dinput 3dextras
QT += widgets
 
SOURCES += main.cpp

QT += 3dcore 3drender 3dinput 3dextras
QT += widgets

SOURCES += main.cpp

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I am using Qt5 LTS version.
Am I forgetting some plugins or am I doing something wrong?
I don't understand why I am getting such runtime error.

Franco