Root aliases in set subqueries are not isolated from one another

[Mobe91]

Consider the following snippet:

.where("cte.id").notIn()
		.from(UserDataPermissionCte.class, "cte1")
		.from(UserPermission.class, "up")
		.select("cte1.id")
		.where("cte1.field").eqExpression("up1.field")
		.where("cte1.entity").eqExpression("up1.entity")
		.where("cte1.actionName").eqExpression("up1.actionName")
		.where("cte1.subjectId").eqExpression("up1.subject.id")
	.unionAll()
		.from(UserDataPermissionCte.class, "cte2")
		.from(UserPermission.class, "up")
		.select("cte2.id")
		.where("up2.field").eqExpression(":emptyField")
		.where("cte2.entity").eqExpression("up2.entity")
		.where("cte2.actionName").eqExpression("up2.actionName")
		.where("cte2.subjectId").eqExpression("up2.subject.id")
	.endSet()
.end()

This results in an exception because up is reported as duplicate alias. This is wrong since the two queries should be isolated.