notification doesn't dissapear after exiting the flashcard

[sotha1]

basically, when my flashcard question notification appear and i enter to answer it and then click the "exit" button, the notification keep showing the flash question notification, but blank. i would like if it just disappears after opening the notification and clicking the "exit" button, because when i see it's icon in my notification bar i think the another question arrived, but not, so i have to every time remove the notification manually. (sorry if you didn't understand me, i'm bad speaking english)