Thank you for that observation. It looks like an oversight to me and should be very easy to add to the next release.
You should be able to disconnect the web signal in the same manner as the Email. I'v enot tested this works, but it might point you in the right direction.
var _webaddr = mywindow.findChild("_webaddr");
toolbox.coreDisconnect(_webaddr, "doubleClicked()", mywindow, "sLaunchWebaddr()");