This might sound like a ridiculous question, but how do I close the 'Edit brush settings' pop-up menu after I've finished with it?

I only ever go in there when I want a brush tip which will give me a different stroke to the brushes that are docked under the colour wheel, but when I've picked my tip there doesn't seem to be any way to close it. I can right click on the grey area just outside my canvas, but this brings up the colour wheel, and if I left click to get rid of it there's a chance it will place an unwanted paint stroke on my canvas.

How exactly do I close this pop-up effectively, when I'm finished with it?

Just press ESC