Bug 163357 [Viewers] NullPointerException on AbstractTreeViewer.remove(path, index)
I20061102-1715 It's possible to get an NPE when removing an element from a tree viewer. The remove API accepts a "parent path" and "child index". It is possible to specify an empty tree path for the parent to indicate the root element. However, the remove code eventually trys to find the widget associated with the "last segment" of the parent path. This results in null, and an NPE: Caused by: java.lang.NullPointerException at org.eclipse.jface.viewers.CustomHashtable.hashCode(CustomHashtable.java:265) at org.eclipse.jface.viewers.CustomHashtable.get(CustomHashtable.java:237) at org.eclipse.jface.viewers.StructuredViewer.findItems(StructuredViewer.java:769) at org.eclipse.jface.viewers.AbstractTreeViewer.internalFindItem(AbstractTreeViewer.java:173) at org.eclipse.jface.viewers.AbstractTreeViewer.internalFindItems(AbstractTreeViewer.java:153) at org.eclipse.jface.viewers.TreeViewer$8.run(TreeViewer.java:1017) at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1326) at org.eclipse.jface.viewers.TreeViewer.remove(TreeViewer.java:1005) at org.eclipse.debug.internal.ui.viewers.model.ChildrenUpdate.performUpdate(ChildrenUpdate.java:62) at org.eclipse.debug.internal.ui.viewers.model.ViewerUpdateMonitor$1.runInUIThread(ViewerUpdateMonitor.java:43) at org.eclipse.ui.progress.UIJob$1.run(UIJob.java:94) at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35) at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:123) ... 20 more
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
* is this viewer's input or an empty tree path, this will replace the root
	 * element at the given index.
	 * <p>
	 * This method should be called by implementers of ILazyTreeContentProvider
	 * to populate this viewer.
	 * </p>
	 * 
	 * @param parentElementOrTreePath
	 *            the parent of the element that should be updated, or the tree
	 *            path to that parent
	 * @param index
	 *            the index in the parent's children
	 * @param element
	 *            the new element
	 * 
	 * @see #setChildCount(Object, int)
	 * @see ILazyTreeContentProvider
	 * @see ILazyTreePathContentProvider
	 * 
	 * @since 3.2
	 */
	public void replace(final Object parentElementOrTreePath, final int index,
			final Object element) {
		preservingSelection(new Runnable() {
			public void run() {
				if (internalIsInputOrEmptyPath(parentElementOrTreePath)) {
					if (index < tree.getItemCount()) {
						updateItem(tree.getItem(index), element);
					}
				} else {