Bug: bind -u shell-backward-word does not unbind the binding

[lockywolf]

Machine: x86_64
OS: linux-gnu
Compiler: gcc
Description:
        It is possible to bind shell-backward-word, but not possible to unbind.

 Bash Version: 5.0
 Patch Level: 16
 Release Status: release

Repeat-By:
        1) bind '"\e\C-b": shell-backward-word' # make binding
        2) bind -P # to check that the binding appeared
        3) bind -u shell-backward-word # to unbind the binding
        4) bind -P # to check that unbinding didn't work
        
Fix:
        I don't know how to fix the problem.
 Configuration Information [Automatically generated, do not change]:
 Compilation CFLAGS: -O2 -fPIC -Wno-parentheses -Wno-format-security
 uname output: Linux delllaptop.lockywolf.net 5.4.21 #1 SMP Wed Feb 19 19:09:47 
CST 2020 x86_64 Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz GenuineIntel GNU/Linux
 Machine Type: x86_64-slackware-linux-gnu

Date: Thu, 27 Feb 2020 21:39:02 +0800
Message-ID: <87k148jgjt.fsf@delllaptop.lockywolf.net>