message: Fix show_dialog field to be checked before setting true
  This matches spotipy implementation
diff: @@ -351,9 +351,11 @@ impl SpotifyOAuth {
  if let Some(state) = state {
  payload.insert("state", state);
  }
  - if show_dialog.is_some() {
  + if let Some(show_dialog) = show_dialog {
  + if show_dialog {
  payload.insert("show_dialog", "true");
  }
  + }
  let query_str = convert_map_to_string(&payload);
  let mut authorize_url = String::from("https://accounts.spotify.com/authorize?");
  