Bug 27491 Cannot add classpath variable to project
build id : 200212020010 The buttons OK and extend... are always disabled in the add variable dialog
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/dialogfields/ListDialogField.java
* Adds an element at a position.
	 */		
	public void insertElementAt(Object element, int index) {
		if (fElements.contains(element)) {
			return;
		}
		fElements.add(index, element);
		if (fTable != null) {
			fTable.add(element);
		}
		
		dialogFieldChanged();
	}	
	/**
	 * Adds an element at a position.
	 */	
	public void removeAllElements() {
		if (fElements.size() > 0) {
			fElements.clear();
			if (fTable != null) {
				fTable.refresh();
			}
			dialogFieldChanged();
		}
	}
		
	/**
	 * Removes an element from the list.
	 */		
	public void removeElement(Object element) throws IllegalArgumentException {