{
  "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "location": {
      "type": "string"
    },
    "storageSettings": {
      "type": "object"
    },
    "machineSettings": {
      "type": "object"
    },
    "osSettings": {
      "type": "object"
    },
    "adminUsername": {
      "type": "string"
    },
    "adminPassword": {
      "type": "securestring"
    },
    "splunkAdminPassword": {
      "type": "securestring"
    },
    "clusterSecret": {
      "type": "securestring"
    },
    "namespace": {
      "type": "string"
    },
    "subnet": {
      "type": "string"
    },
    "templateBaseUrl": {
      "type": "string"
    }
  },
  "variables": {},
  "resources": [],
  "outputs": {}
}

{
  "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "location": {
      "type": "string"
    },
    "storageSettings": {
      "type": "object"
    },
    "machineSettings": {
      "type": "object"
    },
    "osSettings": {
      "type": "object"
    },
    "adminUsername": {
      "type": "string"
    },
    "adminPassword": {
      "type": "securestring"
    },
    "splunkAdminPassword": {
      "type": "securestring"
    },
    "clusterSecret": {
      "type": "securestring",
      "defaultValue": "NA"
    },
    "namespace": {
      "type": "string"
    },
    "subnet": {
      "type": "string"
    },
    "templateBaseUrl": {
      "type": "string"
    }
  },
  "variables": {},
  "resources": [],
  "outputs": {}
}

Make cluster secret parameter optional
Make cluster secret parameter optional
