Prevent shuffle crash

fixes #959

Author: JasonLG1979

connect/src/spirc.rs

@@ -668,15 +668,15 @@ impl SpircTask {
                 self.state.set_shuffle(frame.get_state().get_shuffle());
                 if self.state.get_shuffle() {
                     let current_index = self.state.get_playing_track_index();
-                    {
-                        let tracks = self.state.mut_track();
+                    let tracks = self.state.mut_track();
+                    if !tracks.is_empty() {
                         tracks.swap(0, current_index as usize);
                         if let Some((_, rest)) = tracks.split_first_mut() {
                             let mut rng = rand::thread_rng();
                             rest.shuffle(&mut rng);
                         }
+                        self.state.set_playing_track_index(0);
                     }
-                    self.state.set_playing_track_index(0);
                 } else {
                     let context = self.state.get_context_uri();
                     debug!("{:?}", context);