Sentinel Playbook - Block IP - New | BadRequest The value cannot be null. The action type 'AppendToArrayVariable' only supports values of types 'Float, Integer, String, Boolean, Object'.

**Describe the bug**
I have deployed [Sentinel Playbook - Block IP - New](https://github.com/Azure/Azure-Network-Security/tree/master/Azure%20WAF/Playbook%20-%20WAF%20Sentinel%20Playbook%20Block%20IP%20-%20New) however when the logic app runs it is failing on For Each 4 / Append to array variable 4, generating the BadRequest error below:

BadRequest
The value cannot be null. The action type 'AppendToArrayVariable' only supports values of types 'Float, Integer, String, Boolean, Object'.

The code view for Append to array variable 4 is:
```
{
"type": "AppendToArrayVariable",
"inputs": {
"name": "MatchValue",
"value": "@items('For_each_4')?['Address']"
}
}

```
**Reproduce**
Sentinel has a rule configured to run when a block action is matched in Application Gateway WAF which in turn causes this logic app to run.

**Expected behavior**
I am expecting the IP that was the source of the Block action to be added to the WAF IP block list

**Screenshots**



I'm at a loss as to how to solve this one, hopefully I am missing the obvious - any suggestions appreciated.