CasRealm not cooperating with other realms: Expects all principals to be originating from itself

in CasRealm.doGetAuthorizationInfo(...):

// retrieve user information
SimplePrincipalCollection principalCollection = (SimplePrincipalCollection) principals;
List<Object> listPrincipals = principalCollection.asList();
Map<String, String> attributes = (Map<String, String>) listPrincipals.get(1);

But if I use multiple realms of course the principal could stem from one of the other realms and therefore of course be without parameters and causes an IndexOutOfBoundsException in line 182:
Map<String, String> attributes = (Map<String, String>) listPrincipals.get(1);

Workaround: Override doGetAuthorizationInfo in own subclass and fix.