Need to get the field having only null value using query

Below is the updated query with proper syntax, in the below query we should be getting only the documents which has resolved = "" or resolved = null, which is not happening, I am even getting the resolved = 'abc'. Kindly let me know if I am missing anything or is there any other way to fix this
POST: /index/type/_search

{
"query": {
"filtered": {
"filter": {
"not": {
"filter": {
"missing": {
"field": "resolved"
}
}
}
}
}
}
}