User Registration configuration page throws MissingPropertyException: No such property: url for class

[Former user]

The User Registration configuration page (http://<HOST>/model-repository/configuration/userRegistration) fails to render with the following error:

groovy.lang.MissingPropertyException: No such property: url for class: net.biomodels.jummp.plugins.configuration.UserRegistrationCommand

    at net.biomodels.jummp.plugins.configuration.ConfigurationService.loadUserRegistrationConfiguration(ConfigurationService.groovy:304)

    at net.biomodels.jummp.plugins.configuration.ConfigurationController$_closure14.doCall(ConfigurationController.groovy:128)

    at grails.plugin.cache.web.filter.PageFragmentCachingFilter.doFilter(PageFragmentCachingFilter.java:200)

    at grails.plugin.cache.web.filter.AbstractFilter.doFilter(AbstractFilter.java:63)

    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)

    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)

    at java.lang.Thread.run(Thread.java:744)