Bug 164247 [DataBinding] NPE from ObservableMapLabelProvider when value is null
When a null value is to be returned from getColumnText(...) a NPE is thrown. It's trying to do a toString() on the null value.
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/ObservableMapLabelProvider.java
/*******************************************************************************
 * Copyright (c) 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 ******************************************************************************/
package org.eclipse.jface.databinding.viewers;
import java.util.Set;
import org.eclipse.core.databinding.observable.map.IMapChangeListener;
import org.eclipse.core.databinding.observable.map.IObservableMap;
import org.eclipse.core.databinding.observable.map.MapDiff;
import org.eclipse.jface.viewers.BaseLabelProvider;
import org.eclipse.jface.viewers.ILabelProvider;
import org.eclipse.jface.viewers.ITableLabelProvider;
import org.eclipse.jface.viewers.LabelProviderChangedEvent;
import org.eclipse.swt.graphics.Image;
/**
 * @since 3.3
 * 
 */
public class ObservableMapLabelProvider extends BaseLabelProvider