When logging in with a magnolia user and wrong password info.magnolia.jaas.sp.ldap.LDAPAuthenticationModule#matchPassword:68 results in a NullPointerException. Problem does not occur with LDAP users.

The functionality works well; however the exception is not manager properly.

Steps to reproduce

1. Loggin using a magnolia user and purposely enter a wrong password
2. Note the following stack in the terminal

   ERROR info.magnolia.cms.security.SecuritySupportBase    : Can't login due to:
   javax.security.auth.login.LoginException: java.lang.NullPointerException
   	at info.magnolia.jaas.sp.ldap.LDAPAuthenticationModule.matchPassword(LDAPAuthenticationModule.java:68)
   	at info.magnolia.jaas.sp.ldap.ADAuthenticationModule.validateUser(ADAuthenticationModule.java:56)
   	at info.magnolia.jaas.sp.AbstractLoginModule.login(AbstractLoginModule.java:199)
   	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   	at java.lang.reflect.Method.invoke(Method.java:498)
   	at javax.security.auth.login.LoginContext.invoke(LoginContext.java:755)
   	at javax.security.auth.login.LoginContext.access$000(LoginContext.java:195)
   	at javax.security.auth.login.LoginContext$4.run(LoginContext.java:682)
   	at javax.security.auth.login.LoginContext$4.run(LoginContext.java:680)
   	...