Symptom:

• restoring XML to JIRA 5.2.11 or JIRA 6.0 rc1
• JIRA throws the following error immediately when trying to restore an XML backup data:

  java.lang.NullPointerException
  	at java.util.AbstractCollection.addAll(AbstractCollection.java:303)
  	at com.atlassian.jira.imports.project.util.XMLEscapeUtil.unicodeInPlaceEncode(XMLEscapeUtil.java:201)
  	at com.atlassian.jira.imports.project.util.XMLEscapeUtil.unicodeInPlaceEncode(XMLEscapeUtil.java:154)
  

Steps to Reproduce:

1. Create an issue that has the character 𠡬 as a summary or description
2. Create an XML backup
3. Restore the newly created backup or perform a project import
4. The steps will result in an NPE

This is not reproducible when restoring the same XML backup data into JIRA 5.2.10

Root cause

• invalid characters in the XML backup data

Workaround

• fix the data using the XML cleaner on the entities.xml before importing the clean XML backup data . The guide available at here
• Detail workaround steps at https://confluence.atlassian.com/display/JIRAKB/Project+Import+will+lead+to+NPE
• Upgrade to JIRA 6.0.1