qtdemux: Properly handle edit list in push mode
qtdemux: Properly handle edit list in push mode

If there are empty segments in edit list, demux should
adjust "accumulated_base" to apply it into running time.

https://bugzilla.gnome.org/show_bug.cgi?id=778426

StreamUtils/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good