Make savequeue more robust.

Change-Id: Ie5723ddc7ca4eff7327fb84c221e88422f7ec4b2
diff --git a/src/com/android/music/MediaPlaybackService.java b/src/com/android/music/MediaPlaybackService.java
index 26b2a93..6226150 100644
--- a/src/com/android/music/MediaPlaybackService.java
+++ b/src/com/android/music/MediaPlaybackService.java
@@ -370,12 +370,14 @@
             int len = mPlayListLen;
             for (int i = 0; i < len; i++) {
                 long n = mPlayList[i];
-                if (n == 0) {
+                if (n < 0) {
+                    continue;
+                } else if (n == 0) {
                     q.append("0;");
                 } else {
                     while (n != 0) {
                         int digit = (int)(n & 0xf);
-                        n >>= 4;
+                        n >>>= 4;
                         q.append(hexdigits[digit]);
                     }
                     q.append(";");
@@ -395,7 +397,7 @@
                     } else {
                         while (n != 0) {
                             int digit = (n & 0xf);
-                            n >>= 4;
+                            n >>>= 4;
                             q.append(hexdigits[digit]);
                         }
                         q.append(";");