Bug 294738 [Viewers] (JFace) Assertion for missing LabelProvider in ViewerColumn
ViewerColumn should throw an AssertionException if the LabelProvider is missing for a column to provide a helpful error message.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerColumn.java
*            the new {@link CellLabelProvider}
	 */
	public void setLabelProvider(CellLabelProvider labelProvider) {
		setLabelProvider(labelProvider, true);
	}
	/**
	 * @param labelProvider
	 * @param registerListener
	 */
	void setLabelProvider(CellLabelProvider labelProvider,
			boolean registerListener) {
		if (listenerRegistered && this.labelProvider != null) {
			this.labelProvider.removeListener(listener);
			listenerRegistered = false;
			if (registerListener) {
				this.labelProvider.dispose(viewer, this);
			}
		}
		this.labelProvider = labelProvider;
		if (registerListener) {
			this.labelProvider.initialize(viewer, this);
			this.labelProvider.addListener(listener);
			listenerRegistered = true;
		}
	}
	/**
	 * Return the editing support for the receiver.
	 * 
	 * @return {@link EditingSupport}
	 */