Prevent index out of bounds exceptions in some live HLS scenarios

Can happen if the load position falls behind in every playlist and
when we try to load the next segment, the adaptive selection logic
decides to change variant.

Issue:#5816
PiperOrigin-RevId: 245923006

RELEASENOTES.md

@@ -112,6 +112,8 @@
     ([#5441](https://github.com/google/ExoPlayer/issues/5441)).
   * Parse `EXT-X-MEDIA` `CHARACTERISTICS` attribute into `Format.roleFlags`.
   * Add metadata entry for HLS tracks to expose master playlist information.
+  * Prevent `IndexOutOfBoundsException` in some live HLS scenarios
+    ([#5816](https://github.com/google/ExoPlayer/issues/5816)).
 * Support for playing spherical videos on Daydream.
 * Cast extension: Work around Cast framework returning a limited-size queue
   items list ([#4964](https://github.com/google/ExoPlayer/issues/4964)).

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java

@@ -278,8 +278,7 @@ import java.util.Map;
     long chunkMediaSequence =
         getChunkMediaSequence(
             previous, switchingTrack, mediaPlaylist, startOfPlaylistInPeriodUs, loadPositionUs);
-    if (chunkMediaSequence < mediaPlaylist.mediaSequence) {
-      if (previous != null && switchingTrack) {
+    if (chunkMediaSequence < mediaPlaylist.mediaSequence && previous != null && switchingTrack) {
         // We try getting the next chunk without adapting in case that's the reason for falling
         // behind the live window.
         selectedTrackIndex = oldTrackIndex;
@@ -289,10 +288,11 @@ import java.util.Map;
         startOfPlaylistInPeriodUs =
             mediaPlaylist.startTimeUs - playlistTracker.getInitialStartTimeUs();
         chunkMediaSequence = previous.getNextChunkIndex();
-      } else {
-        fatalError = new BehindLiveWindowException();
-        return;
-      }
+    }
+
+    if (chunkMediaSequence < mediaPlaylist.mediaSequence) {
+      fatalError = new BehindLiveWindowException();
+      return;
     }
 
     int segmentIndexInPlaylist = (int) (chunkMediaSequence - mediaPlaylist.mediaSequence);