Merge pull request #466 from videojs/fix-resetsrc

(development branch) fix calling abort on a sourceBuffer whose mediaSource.readyState != open

@@ -574,7 +574,7 @@ videojs.HlsHandler.prototype.resetSrc_ = function() {
   this.cancelSegmentXhr();
   this.cancelKeyXhr();
 
-  if (this.sourceBuffer) {
+  if (this.sourceBuffer && this.mediaSource.readyState === 'open') {
     this.sourceBuffer.abort();
   }
 };