[bugfix]: set Null values to 0 when cnf.chart.stacked

[normannMarit]

New Pull Request

I removed the condition for the chart.type to be exclusively 'bar', otherwise when we mix types, we get undefined instead of 0 on stacked bars

Before:

After:

Fixes #3811

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes