LDAP Decision Node does not continue through "Fail" flow when Node Fails with exception

Bug description

If authenticating via LDAP Decision node fails with a NPE, this will also fail to continue executing the full tree via the failed route

How to reproduce the issue

Details steps outlining how to recreate the issue

1. Vanilla AM install
2.  Create a new tree called testtree
3. Within the tree I have the following :
   Start > Username > Password > LDAP Decision > True / False > Success / Fail > If FAIL > Choice Collector with a single choice > Fail
   3.1. the Ldap Decision node has the following : 
   Attributes Used to Search for a User to be Authenticated = uid cn
4.  I created two new users as follows :
   Login > Top Level Realm > Identities > Add Identity > 
   User ID = testone
   Password = password 
   Create
5.  Create another user 
   Login > Top Level Realm > Identities > Add Identity > 
   User ID = testtwo
   Password = password 
   > Create > Full Name = testone
6. Then attempt to login using the new testtree 
   http://openam.example.com:8080/openam/XUI/?service=testtree You should see that authentication fails but does not prompt for a choice. (using the choice collector node) 

Authentication Logs have the following exception, which should be caught an continue the flow via the failed route. 

ERROR: searchForUser : Multiple matches found for user 'eliottest'. Please modify search start DN/filter/scope to make sure unique match returned. Contact your administrator to fix the problem

amAuth:07/11/2019 04:15:27:174 PM BST: Thread[http-nio-8080-exec-1,5,main]: TransactionId[93d625d7-6af4-48dd-aea8-7b953aa677f2-19813]

ERROR: Node processing failed

java.lang.NullPointerException

 at org.forgerock.openam.auth.nodes.LdapDecisionNode.authenticateUser(LdapDecisionNode.java:333)

 at org.forgerock.openam.auth.nodes.LdapDecisionNode.process(LdapDecisionNode.java:282)

 at org.forgerock.openam.auth.trees.engine.AuthTreeExecutor.process(AuthTreeExecutor.java:105)

 at org.forgerock.openam.auth.trees.engine.AuthTreeExecutor.process(AuthTreeExecutor.java:149)

 at org.forgerock.openam.core.rest.authn.trees.AuthTrees.processTree(AuthTrees.java:421)

 at org.forgerock.openam.core.rest.authn.trees.AuthTrees.evaluateTreeAndProcessResult(AuthTrees.java:261)

 at org.forgerock.openam.core.rest.authn.trees.AuthTrees.invokeTree(AuthTrees.java:253)

 at org.forgerock.openam.core.rest.authn.RestAuthenticationHandler.authenticate(RestAuthenticationHandler.java:222)

 at org.forgerock.openam.core.rest.authn.http.AuthenticationServiceV1.authenticate(AuthenticationServiceV1.java:164)

 at sun.reflect.GeneratedMethodAccessor97.invoke(Unknown Source) 

Expected behaviour

Flow should fall through the fail route of the LDAP decision node

Current behaviour

Flow fails completely after ldap decision node

Work around

Use authentication chains, LDAP module will fail and continue through chain to the next module