Hey, did you mean that the browser tab more or less 'freezes' when you close the Image Editor? I had that problem too, quite often for a while, but currently I am not experiencing that anymore, I didn't get/apply any updates (using the Stable version) so I don't know how or why it disappeared.
What happened to me was that now and then I couldn't do anything on the browser tab anymore after closing the Image Editor. If I clicked again on the screen, it would give that typical 'program not responding' overlay and the cursor would show a loading sign, and I couldn't do anything no matter how long I waited.
Yes, I would like to know if there is any way to close only the image editor, without closing the entire program, because doing the same thing several times is getting boring. It's a very long game and doing the same thing too many times makes me lose my will. I'm sure there is a way to do it, but I don't know how. I press ctrl+alt+del, but it only gives me the option to close the whole program.