Themes

Essential theme settings are found in
mdl_config_plugins

select * from mdl_config_plugins where plugin = 'theme_essential'

query above shows 1025 rows.


from command line:
mysql -u USER -p'PASSWORD' -e "use DATABASE4MOODLE;select * from mdl_config_plugins where plugin = 'theme_essential';" > ./essentsettings.txt;cat ./essentsettings.txt;wc -l essentsettings.txt

Look at the resulting essentsettings.txt file

In the site I was using to check info (can't share here cause it
has too much info tha needs to remain private, and for me, too much info period (am a function over form kinda guy) the text file had this which looks like the area you might have edited in settings to cause 'white screen of death'.   Your row 1147 might be different ...

1147    theme_essential    customcss    .dimmed,
\na.dimmed:link,
\na.dimmed:visited,
\na.dimmed_text,
\na.dimmed_text:link,
\na.dimmed_text:visited,
\na.dimmed_.categoryname,
\n.dimmed_text,
\n.dimmed_text a,
\n.dimmed_text a:link,
\n.dimmed_text a:visited,
\n.dimmed_text a{
\nfont-style: normal;
\ncolor: #999;
\n}
\n.usersuspended,
\n.usersuspended a,
\n.usersuspended a:link,
\n.usersuspended a:visited,
\n.dimmed_category,
\n.dimmed_category a {
\ncolor: #ececec;
\n}
\n.dimmed_text a {
\ncolor: #ececec;
\n}
\n/*.categoryname a:visited{
\n
\n*/
\n
\n
\n/*
\n
\nHide Top page block - This is good to go
\n
\n*/
\n.categorypicker {
\ndisplay: none;
\n}
\n#coursesearch {
\ndisplay: none;
\n}
\n.box generalbox info{
\ndisplay: none;
\n}
\n
\n.dimmed_category .info .categoryname a:visited{
\nfont-style: normal;
\ncolor: #ececec;
\n}
\n

Above is guess (probably wrong for your site).

Note and 2 cent advice: as I understand it, support for Essential theme is going away in higher versions of Moodle.  Might consider finding another theme now rather then get dependent on something you might not be able to fix in higher versions ... you can't stay at your version of Moodle for ever and ever ... you'll have to upgrade - sooner or later.

Good luck ...

'SoS', Ken

Also ... is your version of PHP too high?

Server: Apache
X-Powered-By: PHP/7.3.5

https://docs.moodle.org/dev/Moodle_3.6_release_notes

PHP version: minimum PHP 7.0.0 Note: minimum PHP version has increased since Moodle 3.3. PHP 7.1.x and 7.2.x are supported too. PHP 7.3.x support is being implemented (@ MDL-63420) and not ready for production with this release.

https://tracker.moodle.org/browse/MDL-63420

'SoS', Ken