Bug 79916 [Viewers] isDisposed check needed in AbstractTreeViewer#internalRemove
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if (expanded != getExpanded(item)) {
                    if (expanded) {
                        createChildren(item);
                    }
                    setExpanded(item, expanded);
                }
            }
            internalSetExpanded(expandedElements, item);
        }
    }
    /**
     * Return whether the tree node representing the given element can be
     * expanded.
     * <p>
     * The default implementation of this framework method calls <code>hasChildren</code>
     * on this viewer's content provider. It may be overridden if necessary.
     * </p>
     * 
     * @param element
     *           the element
     * @return <code>true</code> if the tree node representing the given
     *         element can be expanded, or <code>false</code> if not
     */
    public boolean isExpandable(Object element) {
        ITreeContentProvider cp = (ITreeContentProvider) getContentProvider();
        return cp != null && cp.hasChildren(element);
    }
    
    protected void labelProviderChanged() {