* fix regression where `displayValue` crashes
It regressed in the sense that it now uses `displayValue` for the
`defaultValue` as well, but if nothing is passed it would crash.
Right now, it makes sure to only run the displayValue value on the
actual value and the actual default value if they are not undefined.
Note: if your displayValue is implemented like `(value) => value.name`,
and your `value` is passed as `null`, it will still crash (as expected)
because then you are in charge of rendering something else than null. If
we would "fix" this, then no value can be rendered instead of `null`.
Fixes: #2084
* update changelog
Robin Malfait
46754e637c