Bogus plugin appeared after upgrade

Following an upgrade, a bogus plugin appeared. We'd like to know how to remove it.

{nohup}
1275534345260upload_1c711e_121eb8a73dd_8000_00000416.tmp
Vendor: (unknown)
Plugin Version: 0.0

Uninstall plugin
There were errors loading this plugin. There is more information in the logs.

Cause:
The artifact URI file:/data/backup/confluence_home/plugin-cache/1275534345260upload__1c711e_121eb8a73dd__8000_00000416.tmp is not a valid plugin artifact{nohup}

Clicking on Uninstall produces

{nohup}
org.springframework.orm.ObjectRetrievalFailureException: Object of class [com.atlassian.confluence.plugin.persistence.PluginData] with identifier [1275534345260upload__1c711e_121eb8a73dd__8000_00000416.tmp]: not found
at com.atlassian.confluence.plugin.persistence.hibernate.HibernatePluginDataDao.getPluginData(HibernatePluginDataDao.java:25)
at com.atlassian.confluence.plugin.persistence.hibernate.HibernatePluginDataDao.remove(HibernatePluginDataDao.java:71)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method){nohup}