! There really is no point having the cancel button on the Loading.... popup unless it cancels, and frankly, that seems like a massive waste of effort to do something that probably won't work right anyway (if it already failed for some reason, such that the popup didn't already go away, cancelling the XHR isn't actually likely to help). So just spirit it away instead, and nail Mantis 4962 at the same time.

Signed-off-by: Peter Spicer <sleeping@myperch.org>