Bug 255229 [Viewers] [3.5] NPE in ColumnViewerToolTipSupport
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerToolTipSupport.java
protected boolean shouldCreateToolTip(Event event) {
		if (!super.shouldCreateToolTip(event)) {
			return false;
		}
		boolean rv = false;
		ViewerRow row = viewer.getViewerRow(new Point(event.x, event.y));
		viewer.getControl().setToolTipText(""); 
		Point point = new Point(event.x, event.y);
		if (row != null) {
			Object element = row.getItem().getData();
			ViewerCell cell = row.getCell(point);
			ViewerColumn viewPart = viewer.getViewerColumn(cell
					.getColumnIndex());
			if (viewPart == null) {
				return false;
			}
			CellLabelProvider labelProvider = viewPart.getLabelProvider();
			boolean useNative = labelProvider.useNativeToolTip(element);
			String text = labelProvider.getToolTipText(element);
			Image img = null;
			if (!useNative) {
				img = labelProvider.getToolTipImage(element);
			}
			if (useNative || (text == null && img == null)) {
				viewer.getControl().setToolTipText(text);
				rv = false;
			} else {
				setPopupDelay(labelProvider.getToolTipDisplayDelayTime(element));
				setHideDelay(labelProvider.getToolTipTimeDisplayed(element));
				Point shift = labelProvider.getToolTipShift(element);