[HUST CSE] Access array elements before Cross border inspection

[azure-z77]

DeviceClass_t devClass = MacCtx.NvmCtx->MulticastChannelList[groupID].ChannelParams.Class;
Before executing this line of code, we'd better first check if the array is out of bounds, rather than placing a check after this line of code.
Code modification: Swap the code position to advance the check for array out of bounds to the front of array access

[tencent-adm]

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[azure-z77]

可否拜托review一下（拜托🙏）

[Supowang1989]

这个修改可能需要意法半导体的工程师介入了，LoRaWAN协议是集成在厂商的BSP里面
或者需要看下semtech官方是否处理