fix: Revert change that caused a lot of warning with "cannot find end…

…Time" and hls playback errors (#7239)

Reverts #7184 ("fix:
Add null check for current reference")

See
#7184 (comment)

lib/media/streaming_engine.js

@@ -1503,14 +1503,11 @@ shaka.media.StreamingEngine = class {
         mediaState.stream.segmentIndex,
         'segment index should have been generated already');
 
-    const currentSegment = mediaState.segmentIterator ?
-        mediaState.segmentIterator.current() : null;
-
-    if (currentSegment) {
+    if (mediaState.segmentIterator) {
       // Something is buffered from the same Stream.  Use the current position
       // in the segment index.  This is updated via next() after each segment is
       // appended.
-      return currentSegment;
+      return mediaState.segmentIterator.current();
     } else if (mediaState.lastSegmentReference || bufferEnd) {
       // Something is buffered from another Stream.
       const time = mediaState.lastSegmentReference ?