bug#40056: 26.3; `comment-padright' fails when `comment-padding' is an integer

[bruno cuconato]

Docstring of `comment-padding' variable says: Can also be an integer which will 
be automatically turned into a string of the corresponding number of spaces. 

I'm using Emacs 26, but by inspection I don't expect a different result in 
master.

% emacs -Q --batch --eval '(let ((comment-padding 0)) (comment-padright "-- " 
1))'
Wrong type argument: sequencep, 0

In GNU Emacs 26.3 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.11)
of 2019-12-10 built on buildhw-10.phx2.fedoraproject.org
Windowing system distributor 'Fedora Project', version 11.0.12006000

Configured using:
'configure --build=x86_64-redhat-linux-gnu
--host=x86_64-redhat-linux-gnu --program-prefix=
--disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
--bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
--datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
--libexecdir=/usr/libexec --localstatedir=/var
--sharedstatedir=/var/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
--with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
--with-gpm=no --with-xwidgets --with-modules
build_alias=x86_64-redhat-linux-gnu host_alias=x86_64-redhat-linux-gnu
'CFLAGS=-DMAIL_USE_LOCKF -O2 -g -pipe -Wall -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions
-fstack-protector-strong -grecord-gcc-switches
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic
-fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection'
LDFLAGS=-Wl,-z,relro
PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS GLIB NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS LCMS2

Important settings:
  value of $LC_MONETARY: en_GB.UTF-8
  value of $LC_NUMERIC: en_GB.UTF-8
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix



-- bruno cuconato