BUG: Colorize background of whitespace

[Holger Klene]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2 -flto=auto -ffat-lto-objects -flto=auto 
-ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security 
-Wall
uname output: Linux BX-NB-015 5.15.90.1-microsoft-standard-WSL2 #1 SMP Fri Jan 
27 02:56:13 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu
Bash Version: 5.1
Patch Level: 16
Release Status: release

Description:
The initial bash background is hardcoded to some default (e.g. black) and 
cannot be colorized by printing "transparent" tabs/newlines with ANSI-ESC-codes.
Only after a vertical scrollbar appears, the whitespace beyond the window hight 
will get the proper background color.

Repeat-By:
run the following command line:
clear; seq 50; printf '\e[36;44m\nsome colored\ttext with\ttabs\e[m\n'
Play with the parameter to seq, to keep the line within the first screen or 
move it offscreen.

Reproduced in:
- in Konsole on Kubuntu 23.04
- in the git bash for windows mintty 3.6.1
- in WSL cmd window on Windows 11