Fixes some MySQL 8 Exceptions

[3lding]

Got this error in the contao logs:

[2019-10-24 18:22:40] app.CRITICAL: An exception occurred. {"exception":"[object] (Doctrine\\DBAL\\Exception\\SyntaxErrorException(code: 0): An exception occurred while executing 'SELECT tl_iso_productcache.* FROM tl_iso_productcache WHERE uniqid='[anonymized-id]' AND (keywords='' OR keywords='') AND (expires>1571934160 OR expires=0) AND groups='' LIMIT 0,1':\n\nSQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'groups='' LIMIT 0,1' at line 1 at [anonymized]/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:99, Doctrine\\DBAL\\Driver\\PDOException(code: 42000): SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'groups='' LIMIT 0,1' at line 1 at [anonymized]/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOConnection.php:109, PDOException(code: 42000): SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'groups='' LIMIT 0,1' at line 1 at [anonymized]/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOConnection.php:107)"} []

Maybe my modification is a "dirty hack" but it works with MySQL 8 and the website is loading without any errors.

[aschempp]

Related to #2086, contao/contao#727, contao/contao#847

I actually like this simple fix, but it wont fix everything and everywhere. I wonder if we still need these adjustments with the fixed DBAL implementation, maybe you can test this locally? Unfortunately I don't have MySQL 8 at hand.

[loilo]

The point is that there has not been a release of the DBAL package for almost a year. The fix has been merged, but no version containing it has been published.

[aschempp]

see doctrine/dbal#3674