If you ever encounter with such similar of an error (in my case it occurred on my Ubuntu 20 distro), you may apply the following process to get a fix. 

The error:

Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
apt apt-transport-https apt-utils dpkg libapt-inst2.0 libapt-pkg5.0 ntpdate
oracle-java8-installer oracle-java8-set-default thermald
10 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/4,389 kB of archives.
After this operation, 8,192 B of additional disk space will be used.
Do you want to continue? [Y/n] Y
Preconfiguring packages ...
dpkg: unrecoverable fatal error, aborting:
files list file for package 'linux-generic' is missing final newline
E: Sub-process /usr/bin/dpkg returned an error code (2)

Disclaimer: it worked for me, that doesn’t necessary means that would work same for you! However, you may give it a try.

remove or move the missing file

sudo rm /var/lib/dpkg/info/linux-generic.list

Now you can again reinstall it

sudo apt-get install linux-generic --reinstall

or

sudo dpkg --configure -a
sudo apt update
sudo apt upgrade

(The later one worked, I suppose the first one should work as well)