[O] `org-drill' broken in recent commits git commits

[York Zhao]

Hi there, `org-drill' has broken recently (after git commit
"3380460"), here is the steps
to reproduce the issue:

1. Create a new org-mode buffer with the following contents:

* org-drill test  :drill:
Foo
** Answer
Bar

2. M-x org-drill
3. Press <SPACE>
4. Press `2' and you are stuck there forever until pressing `q' or "C-g".

Thanks,

York