1164 minor: device insertion/removal UI update ...[6911]

[chrisjj]

...fails to update "Available Devices / Plug-ins" Delete button enabled state.

E.g. preventing Delete of the entry for a removed device. Workaround: select a different device, then reselect the one you want to delete.

EDIT(TC): Tracked at http://www.ventismedia.com/mantis/view.php?id=6911