Fix query based parameter has value null when created (#3707)
Fix query based parameter has value null when created (#3707)

* Fix query based parameter value null when created

* Use toString to avoid having 'null' string

alexanderlz/redash,denisov-vlad/redash,alexanderlz/redash,getredash/redash,denisov-vlad/redash,denisov-vlad/redash,getredash/redash,getredash/redash,alexanderlz/redash,denisov-vlad/redash,denisov-vlad/redash,getredash/redash,getredash/redash,alexanderlz/redash