Please note that we are also not able to un-deploy the theme. We are getting the 500 internal server error in the console which is
PHP Fatal error: Uncaught Error: Call to a member function checkLicense() on null in SuiteCRM/modules/MTS_ThemeBuilder/undeploy.php:3\nStack trace:\n#0 ... thrown in SuiteCRM/modules/MTS_ThemeBuilder/undeploy.php on line 3