'list' object has no attribute 'split' on sending webhook event

[Qoyyuum]

{
  "instance_url": "https://iris.local",
  "webhooks": [
    {
      "name": "Discord",
      "trigger_on": [
        "on_postload_ioc_create",
        "on_postload_ioc_update",
        "on_postload_note_create",
        "on_postload_note_update",
        "on_postload_case_create",
        "on_manual_trigger_case",
        
      ],
      "request_url": "https://discord.com/api/webhooks/<redacted>",
      "request_rendering": "markdown",
      "request_body": {
        "embeds": [
          {
            "description": "%DESCRIPTION%",
            "title": "%TITLE%"
          }
        ]
      }
    }
  ]
}

I added the above as a webhook configuration to my Discord server. I created a case and it triggered the following error:

Traceback (most recent call last):
  File "/iriswebapp/app/iris_engine/module_handler/module_handler.py", line 478, in task_hook_wrapper
    task_status = mod_inst.hooks_handler(hook_name, hook_ui_name, data=_obj)
  File "/opt/venv/lib/python3.9/site-packages/iris_webhooks_module/IrisWebHooksInterface.py", line 175, in hooks_handler
    status = self._handle_hook(hook_name, hook_ui_name, data=data)
  File "/opt/venv/lib/python3.9/site-packages/iris_webhooks_module/IrisWebHooksInterface.py", line 238, in _handle_hook
    self._do_web_hook(hook_name, data, hook, server_url)
  File "/opt/venv/lib/python3.9/site-packages/iris_webhooks_module/IrisWebHooksInterface.py", line 412, in _do_web_hook
    request_data = self.map_request_content(hook.get('request_body'), raw_data)
  File "/opt/venv/lib/python3.9/site-packages/iris_webhooks_module/IrisWebHooksInterface.py", line 484, in map_request_content
    keys = value.split('.')
AttributeError: 'list' object has no attribute 'split'