Isolated points on stacked area not shown.

[markov00]

Describe the issue
Independently from the configuration of the point visibility, when you are rendering a stacked area chart with isolated points, the isolated points are not shown

To Reproduce
Steps to reproduce the behavior:

1. Go to local storybook story (isolated data points) and add the stackAccessor property to the chart
2. Go to storybook
3. See the missing isolated data points

Expected behaviour

The isolated data point should always be visible, independentely from the general point visibility.
Only if they are explicly configured to be hidden/disabled we should hide them.

Screenshots

Version (please complete the following information):
Probably since 67.0.0

Additional context
The fact that in the default theme the visibility of the isolated points is configured as 'auto' doesn't change the bahaviour.