Tabbing when the focus is in a button group without a selected radiobutton just passes the focus on to a widget not in the group

Tabbing when the focus is in a button group without a selected radiobutton just passes the focus on to a widget not in the group. This is not consistant with other applications and Qt 3, only if there is a selected button should it tab out of the group, otherwise it should tab over the buttons.

Note: With Qt 4 you must use the arrow keys to select radio buttons; the tab key moves out of the button group. In Qt 3 it was possible to navigate these buttons with the tab key without activating them, which is an important difference.