This option was removed with 4.10 when some of the changes for the introduction of Sequencer that uses the same code.
This was entered originally with ticket UE- 21932 and determined to that it should be part of the design. We’re going to make a case to see if we can get this put back in since it is not invasive and does not require extensive changes, but I cannot guarantee that that will happen.
As far as functionality, when you’re rendering your movie or image sequence out you can close the editor manually and this will still allow the movie/image sequence to render as it always has. This should resolve the immediate issue that you’re having here.