public void closeRootFolder() {
		isActiveProject = false;
		tree.setProjectActive(false);
		GTreeNode oldRoot = root;
		root = new NoProjectNode();
		tree.setRootNode(root);
		oldRoot.removeAll();
	}
Close the root folder for this data tree.
Ghidra/Framework/Project/src/main/java/ghidra/framework/main/datatree/ProjectDataTreePanel.java