SkipNull options is not fully working

[vaasu070]

SkipNull option is working for grouped bar plots only on some conditions.
Please look at the sample code here to observe he unexpected behavior. Bars are overlapping which ideally should not have been. Also tooltip position does not seem right.

[kurkle]

Turning the bg to semitransparent of the first dataset reveals the 2nd bar of 2nd dataset is sized properly, but placed in wrong location:

Error probably happens here, where we are getting the stack index of the dataset and not considering skipNull:

Chart.js/src/controllers/controller.bar.js

Line 488 in b319f2c

const stackIndex = me._getStackIndex(me.index, me._cachedMeta.stack);

A side note, looks like some code still relies on the bars to be at same dataIndex for the same category:

Chart.js/src/controllers/controller.bar.js

Line 312 in b319f2c

const val = item.controller.getParsed(dataIndex)[