fixes for event editor
fixes for event editor

default tag to blank string so we don’t get a React warning about the
input changing from uncontrolled to controlled

try setting start and end time on blur instead of on change to see if
that stops the date picker from disappearing as soon as anything is
changed (https://app.asana.com/0/8055896560428/144449986729036)

Hylozoic/hylo-redux,Hylozoic/hylo-redux