DW 4 Window Used to remain open?

Greetings,

Before my re-install DW 4 used to not allow me to close the whole program by clicking the “X” at the top right. ( i.e. unless I was just in site view )

I obviously answered that “question” wrong when it asked the first time, but now I can’t seem to find the preference that makes sure that 1 window is always open … unless I choose “File/Exit.”

Can someone point me to the place to turn that back on?

Thanks,
Nous