tests/examples/playlist.c: fix inappropriate down-casts in playlist.py
tests/examples/playlist.c: fix inappropriate down-casts in playlist.py

MathieuDuponchelle/PitiviGes,MathieuDuponchelle/PitiviGes,MathieuDuponchelle/PitiviGes,luisbg/gst-editing-services,cfoch/ges,pitivi/gst-editing-services,ahmedammar/platform_external_gst_editing_services,cfoch/ges,cfoch/gst-editing-services,volodymyrrudyi/gst-editing-services,cfoch/ges,freesteph/gst-editing-services,cfoch/gst-editing-services,cfoch/ges,pitivi/gst-editing-services,ahmedammar/platform_external_gst_editing_services,freesteph/gst-editing-services,cfoch/gst-editing-services,volodymyrrudyi/gst-editing-services,pitivi/gst-editing-services,pitivi/gst-editing-services,cfoch/gst-editing-services,volodymyrrudyi/gst-editing-services,freesteph/gst-editing-services,MathieuDuponchelle/PitiviGes,luisbg/gst-editing-services