Add missing getPeriod call to populate period.

The period in this method is most likely prepopulated correctly, but
this assumption is very error-prone and we should populate it locally.

PiperOrigin-RevId: 293345873

library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java

@@ -744,6 +744,7 @@ import com.google.android.exoplayer2.util.Assertions;
       long startPositionUs,
       long startPositionUs,
       long requestedContentPositionUs,
       long requestedContentPositionUs,
       long windowSequenceNumber) {
       long windowSequenceNumber) {
+    timeline.getPeriodByUid(periodUid, period);
     int nextAdGroupIndex = period.getAdGroupIndexAfterPositionUs(startPositionUs);
     int nextAdGroupIndex = period.getAdGroupIndexAfterPositionUs(startPositionUs);
     MediaPeriodId id = new MediaPeriodId(periodUid, windowSequenceNumber, nextAdGroupIndex);
     MediaPeriodId id = new MediaPeriodId(periodUid, windowSequenceNumber, nextAdGroupIndex);
     boolean isLastInPeriod = isLastInPeriod(id);
     boolean isLastInPeriod = isLastInPeriod(id);