[BUG] disabled playlists in MPD CPU spike & hang #539

Describe the bug
No playlists in MPD cause a CPU spike of ncmpcpp & program hang. It isn't possible to move away from the Playlist editor screen.

To Reproduce
Steps to reproduce the behaviour:

1. Press '5' in ncmpcpp

Expected behaviour
Not cause a hang when playlists are disabled, allow moving away from the Playlist editor regardless of playlists configured or not.

Screenshots/Logs
MPD: Stored playlists are disabled

Desktop (please complete the following information):

• OS: Debian 10
• Terminal: konsole & bash
• Version: git's HEAD

Additional context
No contents of ~/.ncmpcpp/config but mpd_password.