I had the same error after upgrading my WordPress version. It is because the theme isn’t compatible with that version of WP. Most likely, you won’t be able to log in.
if you can’t log in – ftp to site or use host’s file manager and rename the /modularity-lite folder
this will bring up default theme for you to log in and test
Not everyone has this folder.
The easiest way to fix this error is to FTP into your site. In your site’s public_html folder, go to wp-content > themes and delete the theme that you had activated. Now, when you go to your site, there will be nothing. However, you can log in from yoursite.com/wp-admin. Either install a new theme or activate the default theme. The theme that you just deleted will most likely not work again, however you can try reinstalling it because a new version may have been released to add support to the current version of WP.
