Return the selected tab item, or null if there is no selection.
@return the selected tab item, or null if none has been selected
@exception SWTException <ul>
<li>ERROR_THREAD_INVALID_ACCESS when called from the wrong thread</li>
<li>ERROR_WIDGET_DISPOSED when the widget has been disposed</li>
</ul>
Return the selected tab item, or null if there is no selection.
@return the selected tab item, or null if none has been selected
@exception SWTException <ul> <li>ERROR_THREAD_INVALID_ACCESS when called from the wrong thread</li> <li>ERROR_WIDGET_DISPOSED when the widget has been disposed</li> </ul>