open in default: error checking for default browser

[nephele]

There was some linking fault that prevented webkit from launching for me.

THe problem is that the error box of which symbol to launch does not actually appear when clicking a URI in an application, this is ignored.

Instead this should either pick another browser if browser #1 WebPositive is out of commision or show the error that happens in the UI.

For reference: tested with Vision, and with AboutSystem(which uses open)

hrev58622