phpMyAdmin inaccessible with 500 error (PHP Fatal error: Exception thrown without a stack frame in Unknown)

Symptoms

A user is unable to access phpMyAdmin as it returns a 500 Internal Server Error without any other noticeable errors being presented.

Description 

The issue could be related to the phpMyAdmin compiled template files. Check to see if the following log file exists for the user (replace $username accordingly):

/home/$username/logs/.php.error.log

Example error messages that may be seen:

[20-Jan-2021 17:57:27 Europe/London] PHP Parse error:  syntax error, unexpected end of 
file in /home/username/tmp/pma_template_compiles_eposany1/
twig/99/9937763182924ca59c5731a9e6a0d96c77ec0ca5ce3241eec146f7bca0a6a0dc.php on line 135

[20-Jan-2021 17:57:27 Europe/London] PHP Fatal error:  Exception thrown without a stack
 frame in Unknown on line 0

Workaround

Move aside the phpMyAdmin compiled template files for the user (replace $username accordingly):

mkdir -vp /home/$username/pma-tmp/
mv -v /home/$username/tmp/pma_template_compiles_$username/ /home/$username/pma-tmp/