Error with DEBUG logging in SimpleApp with isis-module-security

[Luis Miguel Payet]

Hello,

I create a new project from the SimpleApp archetype, version 1.9.0-SNAPSHOT. I 
change the logging to DEBUG in the logging.properties file. I test that the 
application runs properly.

Then I add the isis-module-security add-on following the readme instructions. 
When I run the application, I get an exception as follows:

21:49:23,873  [IsisWicketApplication main       ERROR]  Failed to initialize
com.google.inject.ProvisionException: Guice provision errors:

1) Error in custom provider, java.util.ConcurrentModificationException
  at 
org.apache.isis.core.runtime.runner.IsisInjectModule.provideIsisSystem(IsisInjectModule.java:132)
  at 
org.apache.isis.core.runtime.runner.IsisInjectModule.provideIsisSystem(IsisInjectModule.java:132)
  while locating org.apache.isis.core.runtime.system.IsisSystem
    for field at 
org.apache.isis.viewer.wicket.viewer.IsisWicketApplication.system(IsisWicketApplication.java:142)
  while locating domainapp.webapp.SimpleApplication

When I turn the logging down to INFO, the application runs properly. The same 
behaviour happens with the SimpleApp version 1.8.0

Please help, as I’m far too new at this to be able to fix it myself.

Thanks,
Miguel