修改项说明：

Class/LearningCenter/OnlineLearning/VideoHelperViewController.m

@@ -244,6 +244,7 @@
     [self customDealloc];
     self.playButton.selected = YES;
     self.bufferProgressView.progress = 0;
+    [self.playerLayer removeFromSuperlayer];
     self.playingTimeLabel.text = @"00:00";
 }