fix: Fix hang when seeking to the last segment (#4537)

The fetchAndAppend_ function was not running on the last segment.

AUTHORS

@@ -69,6 +69,7 @@ SameGoal Inc. <*@samegoal.com>
 Sanborn Hilland <sanbornh@rogers.com>
 Sander Saares <sander@saares.eu>
 Sanil Raut <sr1990003@gmail.com>
+Seongryun Jo <ocipap0531@gmail.com>
 Swank Motion Pictures Inc. <*@swankmp.com>
 TalkTalk Plc <*@talktalkplc.com>
 Tatsiana Gelahova <tatsiana.gelahova@gmail.com>

CONTRIBUTORS

@@ -104,6 +104,7 @@ Sandra Lokshina <ismena@google.com>
 Sanil Raut <sr1990003@gmail.com>
 Satheesh Velmurugan <satheesh@philo.com>
 Semih Gokceoglu <semih.gkcoglu@gmail.com>
+Seongryun Jo <ocipap0531@gmail.com>
 Seth Madison <seth@philo.com>
 Tatsiana Gelahova <tatsiana.gelahova@gmail.com>
 Theodore Abshire <theodab@google.com>

lib/media/streaming_engine.js

@@ -1012,7 +1012,11 @@ shaka.media.StreamingEngine = class {
     const timeUntilEnd =
         this.manifest_.presentationTimeline.getDuration() - timeNeeded;
     const oneMicrosecond = 1e-6;
-    if (timeUntilEnd < oneMicrosecond) {
+
+    const bufferEnd =
+      this.playerInterface_.mediaSourceEngine.bufferEnd(mediaState.type);
+
+    if (timeUntilEnd < oneMicrosecond && !!bufferEnd) {
       // We shouldn't rebuffer if the playhead is close to the end of the
       // presentation.
       shaka.log.debug(logPrefix, 'buffered to end of presentation');
@@ -1042,8 +1046,6 @@ shaka.media.StreamingEngine = class {
       return this.config_.updateIntervalSeconds / 2;
     }
 
-    const bufferEnd =
-        this.playerInterface_.mediaSourceEngine.bufferEnd(mediaState.type);
     const reference = this.getSegmentReferenceNeeded_(
         mediaState, presentationTime, bufferEnd);
     if (!reference) {