Something has gone wrong - Theme related error
I foolishly started messing around with Themes via the Dashboard and managed to 'Apply' the wrong theme to the site. Unfortunately, when I tried to re-enable the theme I wanted - 'Bootstrap' - I got the "Something has gone wrong" error.
I tried the trick of changing the theme name from a lowercase b to an uppercase one, Bootstrap not bootstrap and cleared the cache... but sadly the error remains whenever I try and access the [Settings] page in the Dashboard.
Upon checking the error log, I found the following, which sadly means nothing to me!
[09-Feb-2021 16:38:43 UTC] PHP Fatal error: Uncaught Error: Call to a member function getKey() on null in /home/xxxxxxx/public_html/forums/library/Vanilla/AddonManager.php:299
#0 /home/xxxxxxx/public_html/forums/library/core/class.thememanager.php(88): Vanilla\AddonManager->lookupAllByType('theme')
#1 /home/xxxxxxx/public_html/forums/applications/dashboard/controllers/class.settingscontroller.php(1855): Gdn_ThemeManager->availableThemes()
#2 /home/xxxxxxx/public_html/forums/library/core/class.dispatcher.php(872): SettingsController->themes('', '')
#3 /home/xxxxxxx/public_html/forums/library/core/class.dispatcher.php(289): Gdn_Dispatcher->dispatchController(Object(Gdn_Request), Array)
#4 /home/xxxxxxx/public_html/forums/index.php(29): Gdn_Dispatcher->dispatch()
thrown in /home/xxxxxxx/public_html/forums/library/Vanilla/AddonManager.php on line 299
Would someone be kind enough to point me in the direction of a solution please?