public static synchronized void projectClosed(Project project) {
		if (project != null) {
			ProjectLocator projectLocator = project.getProjectLocator();
			ProjectIndexService result = instances.get(projectLocator);
			if (result != null) {
				instances.remove(projectLocator);
				result.close();
			}
		}
	}
Notify the index instance management that a Project has been closed.  Users of this service
need to do this because notification of Project closure is only available to GUI Plugin
classes.

@param project {@link Project} that was closed
Ghidra/Features/Base/src/main/java/ghidra/plugin/importer/ProjectIndexService.java