I am getting below error while provision the servicebus topic subscription. can some one help me to figure this out.

Module code :

resource "azurerm_servicebus_subscription" "subscription" {
  for_each            = { for sb in var.topic_list : "${sb["subscription"]}" => sb }
  name                = each.value["subscription"]
  topic_id            = azurerm_servicebus_topic.topics["${each.value.name}"].id
  max_delivery_count  = var.max_delivery_count
}

variable.tf:

variable "topic_list" {
  type = list(object({
    name                    = string
    max_size_in_megabytes   = string
  }))
  default     = []
}

Inputs values:

topic_list: 
  - name: "topicair"
    max_size_in_megabytes: "5120"
    subscriptions: 
      - subscription: subscription1
      - subscription: subscription2
      - subscription: subscription3
  - name: "topicwint"
    max_size_in_megabytes: "81920"
    subscriptions: 
      - subscription: subscriptiontop1
      - subscription: subscriptiontop2
      - subscription: subscriptiontop3

Error :

Error: Invalid index
│
│   on .terraformmodulesservicebusmodulesservicebusmain.tf line 103, in resource "azurerm_servicebus_subscription" "subscription":
│  103:   for_each            = { for sb in var.topic_list : "${sb["subscription"]}" => sb }
│
│ The given key does not identify an element in this collection value.
╵
╷
│ Error: Invalid index
│
│   on .terraformmodulesservicebusmodulesservicebusmain.tf line 103, in resource "azurerm_servicebus_subscription" "subscription":
│  103:   for_each            = { for sb in var.topic_list : "${sb["subscription"]}" => sb }
│
│ The given key does not identify an element in this collection value.