Bug 255229 [Viewers] [3.5] NPE in ColumnViewerToolTipSupport
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerToolTipSupport.java
if (shift == null) {
					setShift(new Point(DEFAULT_SHIFT_X, DEFAULT_SHIFT_Y));
				} else {
					setShift(new Point(shift.x, shift.y));
				}
				setData(VIEWER_CELL_KEY, cell);
				setText(text);
				setImage(img);
				setStyle(labelProvider.getToolTipStyle(element));
				setForegroundColor(labelProvider
						.getToolTipForegroundColor(element));
				setBackgroundColor(labelProvider
						.getToolTipBackgroundColor(element));
				setFont(labelProvider.getToolTipFont(element));
				
				rv = getText(event) != null || getImage(event) != null;
			}
		}
		return rv;
	}
	protected void afterHideToolTip(Event event) {
		super.afterHideToolTip(event);
		
		setData(VIEWER_CELL_KEY, null);
		if (event != null && event.widget != viewer.getControl()) {
			viewer.getControl().setFocus();
		}
	}
}