Fix keyboard focus for plasmoid
If you open the plasmoid with a shortcut you can use the keys to navigate and launch. Also the index is set to 0 when the plasmoid is launched. Otherwise the previously focused result would be focused and if you used the plasmoid with the mouse there could be no focused item.
And while at it the plasmoid gets closed when a result is activated, it would get closed anyways if the launched kdevelop session gets opened but it feels smoother this way.