Remote copy issue to another project will break if JIRA integrated with LDAP

JIRA Copy feature ( using JIRA to JIRA Copy plugin 3.0 ) failed when JIRA integrated with LDAP.

The problem is reproducible when the following criterias are met:

• JIRA is integrated with LDAP - Delagated LDAP
• The user perform the action (COPY) locally from Project A to project B.

Steps to reproduce:

1. Setup a new JIRA 5.2.11 and integrate it with LDAP
2. Install JIRA to JIRA copy plugin 3.0
3. Create 2 projects - Project A and Project B.
4. Create one issue in project A.
5. Copy the issue by click on Remote Copy More Action -> Remote Copy.
6. The following error is shown.

   java.lang.NullPointerException
   	at com.atlassian.crowd.embedded.impl.IdentifierUtils.toLowerCase(IdentifierUtils.java:42)
   	at com.atlassian.cpji.fields.value.CachingUserMapper.getUsersByEmail(CachingUserMapper.java:64)
   	at com.atlassian.cpji.fields.value.CachingUserMapper.mapUser(CachingUserMapper.java:95)
   	at com.atlassian.cpji.fields.system.AssigneeFieldMapper.mapUser(AssigneeFieldMapper.java:101)
   	at com.atlassian.cpji.fields.system.AssigneeFieldMapper.getMappingResult(AssigneeFieldMapper.java:69)
   	at com.atlassian.cpji.fields.permission.SystemFieldMappingChecker.getFieldPermission(SystemFieldMappingChecker.java:83)
   	at com.atlassian.cpji.components.CopyIssueService.checkFieldPermissions(CopyIssueService.java:257)
   	at com.atlassian.cpji.components.remote.LocalJiraProxy.checkPermissions(LocalJiraProxy.java:151)
   	at com.atlassian.cpji.action.CopyIssueToInstanceAction.doDefault(CopyIssueToInstanceAction.java:503)
   

Finding

• This problem happened in both JIRA 5.1.8 and JIRA 5.2.11.
• Tested using normal and administor user, same problem occurred.
• Testing Remote copy feature without LDAP integration, the problem will be disappear.
• This is not happened in older version of JIRA to JIRA copy plugin during my test using version 3.0-rc1 and 3.0-rc2.