Next/Previous: Next & previous index not computed correctly

When playing an audio track in full screen, the first time the user tries to play the next or the previous track, the next (or previous) index is not computed correctly.

This leads to a reset of the current index, no matter which repeat mode is enabled.

The following screen recordings display the current behaviour when next and then previous button is selected:

When "Do not repeat" mode is enabled

Next_-_No_repeat Previous_-_No_repeat

When "Repeat one" mode is enabled

Next_-_Repeat_one Previous_-_Repeat_one

When "Repeat all" mode is enabled

Next_-_No_repeat Previous_-_Repeat_all