How i can iterate over nested propery in painless elasticsearch script

Elastic Stack Elasticsearch
1

My document mapping looks like this:

                "_source": {
                    "id": 60,
                    "price": 60,
                    "locations": [
                      {
                         "id": 1
                         "price": 70
                      },
                      {
                         "id": 5,
                         "price": 80
                      }
                    ]
                }

So, price field can be both in root and in nested locations array. I want to be able to filter them by both values - if locationId is set in query parameters, then filter by price in locations, else - filter by root price.
I wrote painless script:

			if(params['locationId'] != null){
				for (def location : doc['locations']) {
					if (location.id == params['locationId']) {
						if ((params['lte'] != null || location.price <= params['lte']) && (params['gte'] != null || location.price >= params['gte'])) {
							return true;
						} else {
							return false;
						}
					}
				}
			}
			return (params['lte'] != null || params._source.price <= params['lte']) && (params['gte'] != null || params._source.price >= params['gte']);

And now I'm trying to use it:

            "query": {
                "bool": {
                    "filter": [
                        {
                            "script": {
                                "script": {
                                    "source": "my_script",
                                    "params": {
                                        "locationId": "2"
                                    }
                                }
                            }
                        }
                    ]
                }
            }

But I'm getting an error on second line of my script.
No field found for [locations] in mapping with types []
How can I solve this? I also tried to access locations by params._source.locations, as I do similar in sort scripts, but params are not accessible from filters query