bug#62898: 29.0.90; X can’t be input by the current input method [chinese-ctlaub]

[Van Ly]

Where X is character codepoint

 #x6a58
 #x6a59

with chinese-ctlaub set the current input method, quail-show-key has

 #x6a58 => X can’t be input by the current input method
 #x6a59 => To input ‘X’, type "chaang"

Steps to reproduce
 - emacs -Q
 - switch to buffer in plain Fundamental mode, C-x b bbb
 - M-x set-input-method RET chinese-ctlaub
 - mouse copy, paste the two symbols from chart at row 1, column 2 and 3
 - put cursor over symbol and apply M-x quail-show-key

chart from Shuowen's tree section
 - 
https://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/shuowenRadical.php?rad=%E6%9C%A8

unexpected result
 - the current input method won't learn new input key sequence for symbol

expected result
 - the current input method learns new input key sequence for symbol

The current input method being chinese-ctlaub learns a new input key
sequence for symbol flowing the way a word that does not occur in the
wordlist can be added for future personal spell checking.

bug-gnu-emacs-report.text
Description: bug gnu emacs report