Bug 448990 - Grid throws Exception "Widget is disposed" after
disposeAllItems() in getFocusCell()

Now Grid remove focused item and all selected items.
GridItem, in dispose actions, call the method noRow who remove row index
from object. This operation force invoking Grid.indexOf, which will
throw "Widget is disposed" exception.

Change-Id: I6532a7fb2b70a5b10d850d8ebf50d5c7a0d188d6
Signed-off-by: mpaturzo <caosmpz@yahoo.it>