Taxonomy query returns all terms when not set

[jacobarriola]

Describe the bug
A product attribute is returning all data when a given product is not associated with it instead of null.

I think the issue lies in our resolver when we are setting the values of wc_get_object_terms() to the query args.

Perhaps we should return early if those $term_ids return empty instead of setting the query args to an empty array?

To reproduce
Run the following query, where product with id 123 does not have the Sizes product attribute associated with it and only has Colors.

{
  product(id:123 idType: DATABASE_ID) {
      id
      paSizes {
        nodes {
          name
        }
      }
      paColors {
        nodes {
          name 
        }
      }
    }
}

Expected behavior
paSizes should return null because the given product doesn't have any sizes.

{
  "data": {
    "product": {
        "id": "cHJvZHVjdDo0OTYwNzE=", 
        "paSizes": null,
        "paColors": {
          "nodes": [
            {
              "name": "Blue"
            },
            {
              "name": "Maroon"
            }
          ]
        }
      }
   }
}

Actual behavior
paSizes returns the first 10 sizes.

{
  "data": {
    "product": {
          "id": "cHJvZHVjdDo0OTYwNzE=", 
          "paSizes": {
            "nodes": [
              {
                "name": "W2XL"
              },
              {
                "name": "W2XS"
              },
              {
                "name": "W3XS"
              },
              {
                "name": "WLG"
              },
              {
                "name": "WMD"
              },
              {
                "name": "WSM"
              },
              {
                "name": "WXL"
              },
              {
                "name": "WXS"
              }
            ]
          },
          "paColors": {
            "nodes": [
              {
                "name": "Blue"
              },
              {
                "name": "Maroon"
              }
            ]
          }
        }
    }
}