Bug 5571 JAR Packager: Reveal first checked project
If the list of projects in the JAR Packager is long it is possible that the shown projects are not checked even though there are checked projects (due to current selection). ==> reveal the first checked project.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/CheckboxTreeAndListGroup.java
*	Answer a collection of all of the checked elements in the tree portion
	 *	of self
	 *
	 *	@return java.util.Vector
	 */
	public Set getAllCheckedTreeItems() {
		return new HashSet(fCheckedStateStore.keySet());
	}
	/**
	 *	Answers the number of elements that have been checked by the
	 *	user.
	 *
	 *	@return int
	 */
	public int getCheckedElementCount() {
		return fCheckedStateStore.size();
	}
	/**
	 *	Returns a count of the number of list items associated with a
	 *	given tree item.
	 *
	 *	@return int
	 *	@param treeElement java.lang.Object
	 */
	protected int getListItemsSize(Object treeElement) {
		Object[] elements= getListElements(treeElement);
		return elements.length;
	}
	/**
	 * Gets the table that displays the folder content