fix: 修复 ip 地址登录系统报错，ts 方法兼容旧版本浏览器

easyflow-ui-admin/app/src/views/ai/agents/composables/useAgentTryoutRawRounds.ts

@@ -258,7 +258,7 @@ function selectedVariant(round: AgentTryoutRawRound) {
   return (
     round.variants.find(
       (variant) => variant.variantIndex === round.selectedVariantIndex,
-    ) || round.variants.at(-1)
+    ) || round.variants[round.variants.length - 1]
   );
 }