error of an additional row with empty strings in SQL result for a BigQuery dataset of newyork citibike, citibike trips

Question

I am looking to count the total duration of a particular complete route trip[start station name to end station name] (total_route) in a particular usertype along-with average trip duration (trip_time) for that route and then order it by number of trips (num_trips) in a desc order. Limiting the search by 10 to find the top route by number of trips. The Error can be viewed below when the query results give a row of blank values for usertype, and total_route. I have already looked for blank values in the table by using "IS NULL".

Code:

SELECT 
usertype,
CONCAT(start_station_name,'TO', end_station_name)AS total_route,
COUNT(*) AS num_trips,
ROUND(AVG(tripduration)/60) AS trip_time
FROM `bigquery-public-data.new_york_citibike.citibike_trips` 
GROUP BY start_station_name, end_station_name,usertypeORDER BY num_trips DESC
LIMIT 10

Query results