Mantis Import fails with NPE Exception

Import from Mantis fails with error:

2011-08-16 10:26:20,247 ERROR - Unexpected failure occurred. Importer will stop immediately. Data maybe in an unstable state
java.lang.NullPointerException
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:187)
at com.google.common.collect.SingletonImmutableList.<init>(SingletonImmutableList.java:41)
at com.google.common.collect.ImmutableList.copyFromCollection(ImmutableList.java:297)
at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:260)
at com.atlassian.jira.plugins.importer.external.beans.ExternalIssue.getExternalComponents(ExternalIssue.java:144)
at com.atlassian.jira.plugins.importer.external.ExternalUtils.convertExternalIssueToIssue(ExternalUtils.java:724)
at com.atlassian.jira.plugins.importer.imports.importer.impl.DefaultJiraDataImporter.createIssue(DefaultJiraDataImporter.java:748)
at com.atlassian.jira.plugins.importer.imports.importer.impl.DefaultJiraDataImporter.importIssues(DefaultJiraDataImporter.java:672)
at com.atlassian.jira.plugins.importer.imports.importer.impl.DefaultJiraDataImporter.doImport(DefaultJiraDataImporter.java:298)
at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:25)
at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:14)
at com.atlassian.jira.task.TaskManagerImpl$TaskCallableDecorator.call(TaskManagerImpl.java:359)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at com.atlassian.multitenant.impl.DefaultMultiTenantManager.runForTenant(DefaultMultiTenantManager.java:61)
at com.atlassian.multitenant.juc.MultiTenantExecutors$WrappedRunnable.run(MultiTenantExecutors.java:160)
at com.atlassian.jira.task.ForkedThreadExecutor$ForkedRunnableDecorator.run(ForkedThreadExecutor.java:249)
at java.lang.Thread.run(Thread.java:662)
2011-08-16 10:26:20,247 INFO - Reindexing last 1 issues imported ...