Don't remove all-NA columns; retain NAs in labels

[IndrajeetPatil]

• Closes https://github.com/IndrajeetPatil/ggstatsplot/issues/833
• Closes #176

[codecov[bot]]

Codecov Report

Merging #226 (c055746) into main (4e4f573) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #226   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          513       508    -5     
=========================================
- Hits           513       508    -5     

Impacted Files	Coverage Δ
R/oneway_anova.R	100.00% <ø> (ø)
R/two_sample_test.R	100.00% <ø> (ø)
R/add_expression_col.R	100.00% <100.00%> (ø)
R/helpers_easystats.R	100.00% <100.00%> (ø)
R/print.R	100.00% <100.00%> (ø)
R/tidy_model_expressions.R	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.