Previously, we considered events to have "missing logs" if any of their tasks
did not have a task log. But now we'd like to switch so that we only consider
missing logs if there are no logs attached to the events tasks.
- Event
- task 1
- task log
- task 2
- task 1
This event used to return true for missing_task_log? because task 2 did not
have log. But now it will return false because it has at least one log (on
task 1).