Make DefaultDashChunkSource more robust against empty segment timelines

Segment timelines are technically allowed to be empty, but not all places
add the necessary checks.

Issue: #11014
PiperOrigin-RevId: 514722205

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DefaultDashChunkSource.java

@@ -234,9 +234,12 @@ public long getAdjustedSeekPositionUs(long positionUs, SeekParameters seekParame
  // Segments are aligned across representations, so any segment index will do.
  for (RepresentationHolder representationHolder : representationHolders) {
  if (representationHolder.segmentIndex != null) {
+ long segmentCount = representationHolder.getSegmentCount();
+ if (segmentCount == 0) {
+ continue;
+ }
  long segmentNum = representationHolder.getSegmentNum(positionUs);
  long firstSyncUs = representationHolder.getSegmentStartTimeUs(segmentNum);
- long segmentCount = representationHolder.getSegmentCount();
  long secondSyncUs =
  firstSyncUs < positionUs
  && (segmentCount == DashSegmentIndex.INDEX_UNBOUNDED
@@ -592,7 +595,7 @@ private ArrayList<Representation> getRepresentations() {
  }
 
  private long getAvailableLiveDurationUs(long nowUnixTimeUs, long playbackPositionUs) {
- if (!manifest.dynamic) {
+ if (!manifest.dynamic || representationHolders[0].getSegmentCount() == 0) {
  return C.TIME_UNSET;
  }
  long lastSegmentNum = representationHolders[0].getLastAvailableSegmentNum(nowUnixTimeUs);