Fix premature file close when '3D positions' is run with a dump file.
Fix premature file close when '3D positions' is run with a dump file.

jimmy516/openptv-python,OpenPTV/openptv-python,OpenPTV/openptv-python,jimmy516/openptv-python,jimmy516/openptv-python,OpenPTV/openptv-python,jimmy516/openptv-python