ADE 3.0 - how to turn off question about adding to library?

I've upgraded my ADE to version 3.  But now every time I open an ePub file in ADE, when I close the file ADE asks to add the file to its library.  There's no option to say no, and even though I select the checkbox to not ask the question again, it still asks me every time.

I can still add items manually to the library when I want to, so the question is redundant.

Is there any way to switch this option off once and for all?