检查列表索引在cloudformation中的可用性

Question

如何检查列表索引在cloudformation中的列表中是否可用？

AWSTemplateFormatVersion: 2010-09-09
Parameters:
  s3Buckets:
    Type: String
    Default: "cc-lokesh-test1"
Conditions:
  AppHasLoadBalancerPathPattern: !Not [!Equals [!Select [ 0, !Split [ ",", !Ref s3Buckets ]], '']]
  AppHasLoadBalancerPathPattern1: !Not [!Equals [!Select [ 1, !Split [ ",", !Ref s3Buckets ]], '']]

我在创建堆栈执行时遇到错误：Template error: Fn::Select cannot select nonexistent value at index 1