Importing an Asana project continously fails with the error "java.lang.NullPointerException: name argument cannot be null"

When trying to import a project from Asana into JIRA, the importer always fails with the same error:

Unexpected failure occurred. Importer will stop immediately. Data may be in an unstable state java.lang.NullPointerException: name argument cannot be null

I'll try to attach my log files in a second. For some reason, I can't attach them using the "Create issue" dialog... Our JIRA installation is the latest version, and all Add-Ons are up-to-date.