Presto: ignore blank passwords (#3791)
Presto: ignore blank passwords (#3791)

PyHive expects only None as no password.
alexanderlz/redash,getredash/redash,denisov-vlad/redash,alexanderlz/redash,alexanderlz/redash,getredash/redash,denisov-vlad/redash,getredash/redash,denisov-vlad/redash,getredash/redash,getredash/redash,denisov-vlad/redash,denisov-vlad/redash,alexanderlz/redash