Unable to close File Structure context window with keys

When opening "File Structure" - I believe the default key binding is CTRL+F12 - which opens a context window where I can search for symbols in the file, then I am not able to close the context window without selecting an entry.

I would expect it to close when I hit the escape key, but it does not. I am **forced** to use my mouse and click outside that context window to actually close it. I would like to be able to do so with a key combination.