[Feature Request] Do Not Allow Blank Responses (i.e. Require Something to be Typed Before <Enter >)

Personally, I would like Memrise to require that some character to be typed before one can hit “Enter” while learning or even reviewing words. Sometimes, when my internet connection is slower than normal, I end up hitting enter a second time for a particular word (thinking that I didn’t hit it the first time while the screen is taking a while to refresh), only to then have Memrise accept a completely blank response for the next word. This leads to my getting words marked as incorrect when I actually do know them.

Is anyone else having this problem?