Fix shuffle behavior introduced in #132

The player's current file was not being updated, resulting in always
considering that it was playing the first one when shuffling.

libresonic-main/src/main/java/org/libresonic/player/controller/StreamController.java

@@ -133,6 +133,15 @@ public class StreamController implements Controller {
                     return null;
                 }
 
+                // Update the index of the currently playing media file. At
+                // this point we haven't yet modified the play queue to support
+                // multiple streams, so the current play queue is the real one.
+                int currentIndex = player.getPlayQueue().getFiles().indexOf(file);
+                player.getPlayQueue().setIndex(currentIndex);
+
+                // Create a new, fake play queue that only contains the
+                // currently playing media file, in case multiple streams want
+                // to use the same player.
                 PlayQueue playQueue = new PlayQueue();
                 playQueue.addFiles(true, file);
                 player.setPlayQueue(playQueue);