Cylc UI gets confused if you set a task succeeded, failed, succeeded

[ColemanTom]

Description

Doing cylc set in order (at least of) succeeded, failed, succeeded gives incorrect symbol colouring. The status of outputs appears correct in cylc show, but incorrect (maybe?) in UI.

Reproducible Example

NOTE: Look at UI symbols in between each cylc set command, and on CLI to see the inconsistency.

1. Run any workflow
2. cylc set workflow//cycle/task (circle is fully coloured in)
3. cylc set -o failed workflow//cycle/task (circle now has a cross in it)
4. cylc set workflow//cycle/task (circle has no symbol or colouring)
5. cylc set workflow//cycle/task (circle still has no symbol or colouring)

Expected Behaviour

I think it should be showing as fully coloured in. However, I recognise that it is perhaps in a confused state.