MySQL 5.7.x only_full_group_by Error

[vytux-com]

After upgrading my server to MySQL 5.7 builds I am getting some errors in webtrees code and also some of my modules. Here is one example:

#0 /app/Statement.php:82 PDOException("SQLSTATE[42000]: Syntax error or access violation: 1055 Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vytux_webtrees.wt_dates.d_type' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by")
#1 /app/Statement.php:129 execute()
#2 /app/Functions/FunctionsDb.php:952 fetchAll()
#3 /app/Module/ResearchTaskModule.php:114 getCalendarEvents()
#4 /var/www/webtrees/webtrees-1.7.1/index.php:132 getBlock()

[fisharebest]

Looking at this SQL, I am not sure we need the "GROUP BY". We already group the results in PHP.