fix (demo): Corrected inconsistencies in the divergent bar stacks demo.

[v-ein]

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name: Pull Request about: Create a pull request to help us improve title: Corrected inconsistencies in the divergent bar stacks demo. assignees: @v-ein

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Description: The Bar Stacks section of demo.py contains incorrect references to labels_div/labels_reg, which leads to an exception when the user clicks the Divergent check box. Here's the error that occurs:

Message:   `values` size 120 must be a multiple of `group_size` 9

This PR corrects the references.

Kudos to @QuattroMusic for finding it!

Concerning Areas: None.