Fix categorial regression

[hoxbro]

Fixes #5835

Fixes #5842

[codecov-commenter]

Codecov Report

Merging #5850 (f360ff8) into main (5ba6537) will increase coverage by 0.11%.
Report is 6 commits behind head on main.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5850      +/-   ##
==========================================
+ Coverage   88.23%   88.34%   +0.11%     
==========================================
  Files         309      310       +1     
  Lines       63915    63930      +15     
==========================================
+ Hits        56396    56480      +84     
+ Misses       7519     7450      -69     

Flag	Coverage Δ
ui-tests	23.39% <30.00%> (+0.03%)	⬆️

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Files Changed	Coverage Δ
holoviews/plotting/bokeh/element.py	88.06% <100.00%> (+0.02%)	⬆️
holoviews/plotting/mixins.py	83.23% <100.00%> (ø)
holoviews/tests/plotting/bokeh/test_barplot.py	100.00% <100.00%> (ø)

... and 18 files with indirect coverage changes

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[philippjfr]

Would love top see a test added here, otherwise this looks good.