Mongo Aggregation to replace an empty / null array field inside an array with a default array

I have a collection like below

{
    relatedProperties: [ //Array
       {
            locations: [ //Array 
                {
                    value: "Brazil"
                },
                {
                    value: "Germany"
                }
            ]
       },
       {
            locations: []
       },
       {
            locations: null
       }
    ]
}

How do I write an aggregation to make only the empty or null arrays to have a default value like;

locations: [  
                {
                    value: "India"
                }
           ]