Added a null check. closes #581

@@ -323,6 +323,7 @@ const filterBufferedRanges = function(predicate) {
     // report a fully empty buffer until SourceBuffers have been created
     // which is after a segment has been loaded and transmuxed.
     if (!this.mediaSource ||
+        !this.mediaSource.mediaSource_ ||
         !this.mediaSource.mediaSource_.sourceBuffers.length) {
       return videojs.createTimeRanges([]);
     }

@@ -777,6 +777,13 @@ QUnit.test('always returns an empty buffered region when there are no SourceBuff
   QUnit.equal(this.player.tech_.hls.findBufferedRange_().length,
               0,
               'empty TimeRanges returned');
+
+   // Simulate the condition with no media source
+  delete this.player.hls.mediaSource.mediaSource_;
+
+  QUnit.equal(this.player.tech_.hls.findBufferedRange_().length,
+              0,
+              'empty TimeRanges returned');
 });
 
 QUnit.test('finds the correct buffered region based on currentTime', function() {