Bug 143659 [Accessibility] Press Tab key will cause eclipse crash when focus isn't on any report item in Editor view
Press Tab key will cause eclipse crash when focus isn't on any report item in Editor view Steps to reproduce: 1. New a report 2. Click the blank area in Layout of Editor view 3. Press Tab key Expected result: Something in layout will get focus Actual result: Eclipse crashed
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/editors/parts/ReportFocusTraverseManager.java
* If this child is focusable, return it
			 * If not focusable, traverse to its sibling and repeat.
			 * If there is no sibling, traverse its parent.
			 */
			if (siblingPos != 0) {
				nextFocusOwner = ((IFigure)(siblings.get(siblingPos - 1)));
				if (isFocusEligible(nextFocusOwner))
					found = true;
				
			} else {
				
				nextFocusOwner = ((IFigure)(siblings.get(siblings.size() - 1)));
				if (isFocusEligible(nextFocusOwner))
					found = true;
				
			}
		}
		return nextFocusOwner;
	}
	
	
	/**
	 * Returns the IFigure that will receive focus upon a 'shift-tab' traverse event.
	 * 
	 * @param root The {@link LightweightSystem LightweightSystem's} root figure
	 * @param focusOwner The IFigure who currently owns focus 
	 * @return the previous focusable figure
	 */
	public IFigure getPreviousFocusableFigure(IFigure root, IFigure focusOwner) {