groupMode should be undefined if no groupby is set on the secondary
axis!
This default value is also the reason -- all the logic -- where
groupMode was checked for conditional rendering -- for eg
, negative data labels when there is no groupby -- the labels should
appear below wasn't happening -- since there was always a default to
groupMode!
changes -
- getting rid of the default value on the bar chart DTO for groupMode
- on front -- make sure groupMode is only set when the secondary axis
gets groupBy id and proper cleanup
