#vulnerable code 
                             private Set<String> userRoles(Req req, String username) {
		if (username != null) {
			try {
				return req.routes().custom().rolesProvider().getRolesForUser(req, username);
			} catch (Exception e) {
				throw U.rte(e);
			}
		} else {
			return Collections.emptySet();
		}
	} 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             private Set<String> userRoles(Req req, String username) {
		if (username != null) {
			try {
				return Customization.of(req).rolesProvider().getRolesForUser(req, username);
			} catch (Exception e) {
				throw U.rte(e);
			}
		} else {
			return Collections.emptySet();
		}
	}