Audio player: global progress indicator is empty

Description

When playing only one track, the progress is empty but still visible.

OP: https://forum.videolan.org/viewtopic.php?f=35&t=157428&p=517944&sid=70136f23c0d44fe8cd4cf0d5c86875d3#p517944

Expected behavior

Actual behavior

Steps to reproduce

1. Start a play queue of 2 tracks
2. Remove one track

Screenshot / video

Context

App version

master

Android version

Device model

App mode

Smartphone

changed milestone to %3.4.x

closed with commit 4005c13c