linux-image-5.8.0-53-generic E: Sub-process /usr/bin/dpkg returned an error code (1)

Question

I was trying to install AnyDesk on my Ubuntu 20.04 and ran this command in the shell -

abhilash@friday:~$ sudo apt-get upgrade

And it returned:

   Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be REMOVED:
  linux-image-5.8.0-53-generic
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 9,822 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 385266 files and directories currently installed.)
Removing linux-image-5.8.0-53-generic (5.8.0-53.60~20.04.1) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-5.8.0-53-generic
/etc/kernel/postrm.d/zz-update-grub:
Sourcing file `/etc/default/grub'
/usr/sbin/grub-mkconfig: 8: /etc/default/grub: 2: not found
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 127
dpkg: error processing package linux-image-5.8.0-53-generic (--remove):
 installed linux-image-5.8.0-53-generic package post-removal script subprocess returned error exit status 1
dpkg: too many errors, stopping
Errors were encountered while processing:
 linux-image-5.8.0-53-generic
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)

I saw this error message already addressed on the forum here but the discussion did not help me as I am running Ubuntu without dual-boot and don't have any antivirus softwares that might have caused the issue (according to the discussion on the question).

Since the package linux-image-5.8.0-53-generic looks associated with the os/kernel, I did not fiddle much with it but have already tried all the methods mentioned on https://itsfoss.com/dpkg-returned-an-error-code-1/ but so far nothing has worked out.

I am currently able to access all of my data and able to reboot my system as well but would like to solve this problem as I am unable to install new packages.

Looking forward to any suggestions from the community.

Update: As pointed out by @user535733, I am sharing my /etc/default/grub file

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'
GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT= 10
GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
Uncomment to enable BadRAM filtering, modify to suit your needs
This works with Linux (no patch required) and with any kernel that obtains
the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
The resolution used on graphical terminal
note that you can use only modes which your graphic card supports via VBE
you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"
Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"