Auto-select first value in Scenario Mail reporter Channel field

A lot of our users make the same mistake when creating a Scenario Mail reporters, they leave the Channel field as is. Unlike most other drop down fields in Dataiku the Channel drop down in a Scenario Mail reporter defaults to "Nothing selected". This results in the scenario mail reporter not having a valid channel selected and never being able to run even though Dataiku allows the user to save the reporter with all the other parameter filled. We would like this field to default to the first Channel configured in DSS. Most installations will probably have a single SMTP channel configured so this should improve the UX for users that don't know they need to select a channel.