openscad no-spline

Saved backup file: C:/Users/dpantazis/Documents/OpenSCAD/backups/logo-test-backup-Uhgq5952.scad
Compiling design (CSG Tree generation)...
Compiling design (CSG Products generation)...
WARNING: Unsupported DXF Entity 'SPLINE' (1) in layer '0' of "dragon-logo.dxf".
ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion violation! Expr: e->incident_sface() != SFace_const_handle() File: /opt/mxe/usr/x86_64-w64-mingw32.static/include/CGAL/Nef_S2/SM_const_decorator.h Line: 326
Geometries in cache: 64
Geometry cache size in bytes: 2853040
CGAL Polyhedrons in cache: 9
CGAL cache size in bytes: 5828176
Compiling design (CSG Products normalization)...
Normalized CSG tree has 1 elements
Compile and preview finished.
Total rendering time: 0 hours, 0 minutes, 0 seconds