Fixed Spoiler is not inserted when press enter on a keyboard

Affected version
2.0 Beta 7
Steps to reproduce:
  1. Open any thread.
  2. Go to the reply form.
  3. Insert -> Spoiler.
  4. Press enter on a keyboard.
Result: spoiler is not inserted.

Expected: spoiler should be inserted without the title.

Workaround: click on the continue button, an empty spoiler will be inserted as expected.

Happens on the latest Google Chrome (both WIN and MAC).