fraction-with-notes problem as of version 2.21.0

[Jacques Menu]

Hello folks,

This snippet taken from LPNR 2.19.82 is handled alright by the latter, but 
fails with 2.21.0:

%%%%%%%
\version "2.21.0"

\relative c'' {
  \once \override TupletNumber.text = #(tuplet-number::fraction-with-notes "4." 
"8")
  \tuplet 3/2  { c4. c4. c4. c4. }
}
%%%%%%%

Starting lilypond 2.21.0 [foo.ly]...
Processing `/home/user/libmusicxml-git/files/samples/musicxml/foo.ly'
Parsing...
Interpreting music...
Preprocessing graphical objects...
Finding the ideal number of pages...
Fitting music on 1 page...
Drawing systems...
fatal error: make-note-markup: Invalid argument in position 1.  Expect: 
duration, found: "4.".
Exited with return code 1.

Has something changed in that area in 2.21.0?

Thanks for your help!

JM