Fixed appendUntilEventFires to stop at the end of media segments

User agents may prioritize appending media segments over the underlying
operation and expected event that the function is waiting for. The method
could crash when it reached the end of available media segments to add.

media-source/mediasource-util.js

@@ -296,7 +296,7 @@
 
         var i = startingIndex;
         var onAppendDone = function() {
-            if (eventFired)
+            if (eventFired || (i >= (segmentInfo.media.length - 1)))
                 return;
 
             i++;