NowPlaying reorderable sources work again

Fixes issue 2569

Change-Id: I891bbbd1d2d66d889f6728e08ef7921131096b45
Reviewed-on: http://gerrit.dmdirc.com/576
Automatic-Compile: Gregory Holmes <greboid@dmdirc.com>
Reviewed-by: Gregory Holmes <greboid@dmdirc.com>

src/com/dmdirc/addons/nowplaying/NowPlayingPlugin.java

      */
     public MediaSource getBestSource() {
         MediaSource paused = null;
+        final List<MediaSource> possibleSources = getSources();
         
-        Collections.sort(sources, new MediaSourceComparator(order));
+        Collections.sort(possibleSources, new MediaSourceComparator(order));
         
-        for (final MediaSource source : getSources()) {
+        for (final MediaSource source : possibleSources) {
             if (source.getState() != MediaSourceState.CLOSED) {
                 if (source.getState() == MediaSourceState.PLAYING) {
                     return source;