Fix HLS chunkful preparation bug affecting certain master playlists

The bug affects playlists that start with an I-FRAME only variant.

Issue: #8025
PiperOrigin-RevId: 335819497

RELEASENOTES.md

@@ -51,6 +51,10 @@
         ([#7988](https://github.com/google/ExoPlayer/issues/7988)).
     *   Ignore negative payload size in PES packets
         ([#8005](https://github.com/google/ExoPlayer/issues/8005)).
+*   HLS:
+    *   Fix crash affecting chunkful preparation of master playlists that start
+        with an I-FRAME only variant
+        ([#8025](https://github.com/google/ExoPlayer/issues/8025)).
 *   IMA extension:
     *   Fix position reporting after fetch errors
         ([#7956](https://github.com/google/ExoPlayer/issues/7956)).

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

@@ -592,7 +592,9 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
     public InitializationTrackSelection(TrackGroup group, int[] tracks) {
       super(group, tracks);
-      selectedIndex = indexOf(group.getFormat(0));
+      // The initially selected index corresponds to the first EXT-X-STREAMINF tag in the master
+      // playlist.
+      selectedIndex = indexOf(group.getFormat(tracks[0]));
     }
 
     @Override