fix: prevent 'called pause from invalid state' warning

[ThomasFrans]

Calling pause() on the Librespot player while it is already paused generates a warning. Don't call pause when the player is already paused.

Describe your changes

• Don't send Pause to the player when it's already paused during queue setup

Issue ticket number and link

Checklist before requesting a review

• Documentation was updated (i.e. due to changes in keybindings, commands, etc.)
• Changelog was updated with relevant user-facing changes (eg. not dependency updates,
  not performance improvements, etc.)

[ThomasFrans]

I think this is correct, but the code still seems a bit weird to me. I don't understand why it calls pause() on the Spotify struct if the song was loaded with start_play set to true. From what I understand, it would only need to check for the PlaybackState::Stopped case and stop the player if it matches. The others are all handled by loading with playback_state == PlaybackState::Playing. I don't fully understand how PlaybackState::Default works so I might be wrong here.