The include empty rows parameter lets you omit rows without data from your Core Reporting API query response. Try it when you’re making a request and expect that the number of valid rows is going to be much smaller than the number of expected dimension values.
This parameter is optional and defaults to true. If set to false, rows without data will be omitted from the response.
Check out the details in the docs: https://goo.gl/eABkwG