Bug 172019 [Viewers] Plus sign doesn't disappear when using deferred content providers
3.3 M4 Use a tree viewer with a content provider using IDeferredWorkbenchAdapter and DeferredTreeContentManager. When fetchDeferredChildren is call and no elements are reported to the element collector the plus sign of the node doesn't disappear. This work without problems under Windows and Mac/OS (e.g. the plus sign disappears).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if (widgets.length == 0) {
			return;
		}
		for (int i = 0; i < widgets.length; i++) {
			internalAdd(widgets[i], parentElementOrTreePath, childElements);
		}
	}
	/**
	 * Find the items for the given element of tree path
	 * 
	 * @param parentElementOrTreePath
	 *            the element or tree path
	 * @return the items for that element
	 *
	 * @since 3.3
	 */
	final protected Widget[] internalFindItems(Object parentElementOrTreePath) {
		Widget[] widgets = findItems(parentElementOrTreePath);
		if (parentElementOrTreePath instanceof TreePath) {
			TreePath path = (TreePath) parentElementOrTreePath;
			Widget w = internalFindItem(path);
			if (w == null) {
				widgets = new Widget[] {};
			} else {
				widgets = new Widget[] { w };
			}
		} else {
			widgets = findItems(parentElementOrTreePath);
		}