Ensure right tasks dropped down when toggling 'show all tasks'

[jacob720]

There is also a bug that I have found:

1. Drop down a task
2. Select Show historic tasks
3. The task that has been dropped down changes

It looks like which is dropped down is tied to index rather than task. I don't think this is a massive bug so if you want to spin it into a new issue then go for it

Originally posted by @DominicOram in #104 (review)