[Bug]: `tm_g_distribution` module report is disabled when selecting "group by"

[averissimo]

What happened?

How to reproduce:

• Run example app
• Select a "Group by" variable
• "+ Add to report" says that there is an error

sessionInfo()

Relevant log output

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[averissimo]

This doesn't change the need to refactor this function, however, it solves the current problem.